texts:
When you say the Venereal Disease Research Laboratory test (VDRL) has a specificity of x% and sensitivity of y%, what are you comparing to? What is considered as the truth?

Because, Wikipedia says, even a gold standard needn't be perfect. It is just the best test available(?). It too has its specificity and sensitivity (<100%)

So, my question is, when we say that the VDRL has a 75% sensitivity, what are we comparing it to? Is it the clinical diagnosis of syphilis according it the case definition? Wouldn't it be much less accurate?


texts: Does the right ventricle affect blood pressure in pulmonary veins?

texts:
Now, I know there are multiple things that push the blood through the entire pulmonary circulation like the contraction of arterial muscular walls... But what I want to know is whether the right ventricle pumps the blood even through the pulmonary veins, or whether its effect stops at the arteries.

This may not be of significance to be honest, but I got into a debate with a friend over this and thought people here would end this debate :)


texts: Factors on which one compound transforming to another compound depend

texts:
Considering the Metabolic Pathway:
http://www.genome.jp/kegg-bin/show_module?M00166
Consider the reaction R01523(the very first reaction). How is it possible to know that the compound  C00199(D-Ribulose 5-phosphate) will get transformed to C01182(D-Ribulose 1,5-bisphosphate)? What are the factors on which this transformation depends?One factor I know is structure but how does structure effect this transformation? Does two similar structured compound means that one of the compound can get transformed to the other one?


texts: In a resting cell at steady state, is sodium influx or potassium efflux higher according to the concentration gradients and permeability, and given that the sodium potassium ATPase is active?


texts: Given that we (humans) are not evolutionarily closely related to bees, why do we find flowers attractive?


texts:
Life on earth started about 3.5 billion years ago. I would assume abiogenesis happened because the conditions were right.

Would the current earth conditions allow for new abiogenesis and completely independent (in terms of phylogeny, not ecology)?


texts: If body temperature is 37°C (98.6°F), why are most people more comfortable at around 21°C (70°F)?

texts:
It may be different for other people, but for me, anything above 32°C (90°F) is very uncomfortable, and my body is inclined to seek cooler temperatures.  But I would think that at 32°C, the body would have less work to do to get itself to 37°C.  So why is it not comfortable in those temperatures?

My theory is this, but I don't know if it's right:

The body's abilities for warming itself are much more sophisticated than its abilities for cooling itself (which are non-existent, possibly?). So it likes to be in an environment 20-30 degrees below optimal because it can easily handle that.  But up in the 32's and we're dangerously close to going over the optimal, and the body doesn't know how to get it back down after that, so we are inclined to seek safer temperatures.

Is it something like that?


texts:
I am a senior in high school and I am studying cystic fibrosis.

I don't quite get the function of the CFTR gene as this is my first time dealing with this type of heavy scientific  info.

I had searched up its function on a website like this:
http://omim.org/entry/602421?search=cystic%20fibrosis&highlight=fibrosi%20cystic

By reading the gene functions section, I learned that CFTR regulate the formation of a chloride channel, changes the regulation of other transport pathways (i.e increase sodium ion absorption in sodium ion absortion). At the same time it also regulate the chloride-coupled bicarbonate receptor. And that is about all I got from that section.

I would greatly appreciate if someone can summarize all the functions of the CFTR gene listed in layman terms (i.e grandma language)  and also explain to me why decreased  chloride channel leads to thicken mucus or increase sodium ion absorption leads to CF Symptoms. In addition I would also appreciate it if someone can tell me does decreased CFTR gene function also lead to other diseases on top of Cystic fibrosis.

Thanks


texts: Is it possible to rank standardized beta coefficients in general linear mixed model?

texts:
I have an experimental treatment at 15 sites and would like to build models to associate usage rates of 4 species with a set of 6 explanatory variables. In the end, I would like to rank the importance of these variable for each species.
Ordinarily, I would simply fit the models and then standardize the beta coefficient by dividing by the standard error and ordering by absolute value.
However, in this case, I need to model a random effect of site and my response variable must be modeled as zero-inflated Poisson, which takes me outside of the realm in which I've seen this comparative analysis performed.

Is there an analogous procedure to ranking standardized beta coefficients for generalized linear mixed models?

Much thanks in advance!

Is it possible to rank standardized beta coefficients in generalized linear mixed models?


texts: How common is bacterial mediated transformation? In plants? In animal cells?

texts:
The most common method to transform plants is by soaking plant tissue in cultures of agrobacteria (this is not their current classification) which transfer DNA into the plants.

Is lateral gene transfer ability like this found a lot in nature?  Is agrobacterium tumificans especially good at this or is its use in plant genetics only because this strain is well studied?

Is a method like this used for animal cells at all?


texts: How can you improve solubility of colloidally dispersed substances?

texts:
If you solve collidally dispersed substances then the particles can form large colloids. This may block narrow passages and diffusion into dense structures may become completely impossible.

What can you do to improve the solubility of such substances?


texts: How is trangender female different from normal female biologically?

texts: I have read in many places that transgender people are usually people who are born with typical male or female anatomies but feel as though they've been born into the “wrong bodies.” The thing that I am confused about is that how someone can not be considered as normal just because he thinks he should not be what he is? I met a female who looked exactly like a normal female and she was very beautiful. She didn't know that she was a transgender till her mom told her that she was transgender when she became adult. What is biological difference between a transgender and a normal male/female?


texts:
Would like to get spiders identified . Specimens can be sent for detailed examination if required .

Spider seen on floor inside house - at Phoenix USA

White off color spider on twigs and flowers of oleander tree with white flower in backyard of house at phoenix USA  - seen dropping off on disturbance and camoflouging with. White flowers. Picture can be magnified spider sitting on green stalk  below brownish dried flowers.


texts: Why do many DNA solutions contain additional compounds?

texts:
DNA solubility data in only water is scarce.
A previous question asked for a quantification of DNA solubility in water. It seemed like it would be easily answerable, however isn't quite that simple since no data seems to exist for DNA solubility in exclusively water.
Even the small amount of data about water was in the context of washing away organic compounds from the solution. This got me thinking. DNA is in an aqueous solution in biological situations, and is usually handled in aqueous solutions in labs. So why is solubility data so scarce for pure water? What is important about organic compounds for DNA solutions?
Why are other additives important for laboratory DNA solutions?
So my question is why is DNA dissolved in exclusively water seemingly "uncommon" in laboratories? Is there something about pure water that is bad for DNA storage? Is it that functionally DNA never needs to be in water because it is inaccessible to proteins? Or have I misinterpreted the lack of solubility data; water is common-place and no data exists because there is no need?
I imagine PCR is where most of the data on DNA solutions exists. What about the polar organic solvents/compounds makes them important for DNA solutions?


texts: why on hydrolysis ATP bond releases energy?

texts: While studying respiration all i came across was that ultimately all that cell does is for the energy currency the ATP and some useful intermediates used in the cell building but i could not figure out how contrary to the notion of supplying energy to break a bond is energy released when the phosphate bonds in ATP are broken .


texts: Why did we evolve to control our breath?

texts:
I had this question in my mind and tried to think of why we would evolve to be able to control our breath. I remembered the Aquatic Ape Hypothesis, which makes a lot of sense and would explain it, though it is not a confirmed scientific theory (but that is another topic).
I also found this question, but it has not been answered properly. A Google search hasn't given me much either.

So my question is, what is the current scientific thinking on this topic (if there is one)?

edit I know that the Aquatic Ape Hypothesis is not a scientific theory. I did not ask anything about it, I only brought it up because it came up a lot when I was looking for an answer to my question. I do not want "maybe this is why it evolved", I was more interested in some creditable scientific paper or something similar.


texts: How some virus are able to reach the CNS?

texts:
I know that the lymphocytic choriomeningitis virus (LCMV) could provoke meningitis and encephalitis when this virus reaches the brain. However, there are other viruses like Varicella (VSV), Cytomegalovirus (CMV) or Herpes (HSV) that are able to reach the brain, hence, to pass trough the blood-brain barrier (BBB) and damage the central nervous system (CNS).

1) Since the blood-brain barrier allows only the free diffusion of some molecules such as water, some gasses and lipid soluble molecule, I was wondering by which mechanism a virus is able to pass trough the BBB.

2) Since the CNS is an immuno-privileged space (where basically the immune system is down-regulated), how does the body eliminate a virus that had reached the brain?


texts: denovo 2Gb whole genome sequencing on a small sequencer

texts:
What are the limitations of using Illumina's smaller sequencers (e.g., iSeq100, miniSeq) to do de novo whole genome sequencing on an organism with a larger genome (~2Gb)?

Naively, it seems even if I am only able to do 5Mb worth of sequencing per 24 hour run on these sequencers, after about two years of running the thing continuously, I should be able to have enough reads to be able to assemble a de novo genome sequence of a larger eukaryote (downstream bioinformatics concerns aside). Yet clearly the sequencers are never marketed like this and I'm struggling to understand why.

I am interested in GWAS on non-model vertebrates if that matters. That time frame doesn't seem crazy, as some field experiments take several years before something is publishable.


texts:
I have had trouble purifying very large quantities of pure PCR product. We are using these as templates for the reconstitution of nucleosomes and I require hundreds of micrograms to milligrams of template.

Here are some methods I have tried:

1) QiaexII slurry--typically I use the entire slurry for one purification then regenerate the resin by washing in 1M HCl then re-equilibrating with water. This way has worked best for me so far but the yield tends to be fairly low (~100 ug from 100 PCR reactions).

2) Phenol-chloroform extraction. This method seemed to work great, however I believe I have phenol contamination at the end--the yields are often much higher than they should be even if I chloroform back extract before the ethanol precipitation. When I run it out on a gel it looks like the apparent concentration I get is off. I have not tried this too many times so perhaps it could be optimized.

3) Spin column purification. I've used the DNA Clean and Concentrator from Zymo and the yields seemed quite low, even for the columns with an apparent 100 ug capacity.

Another option I have explored is large scale purification of the parent plasmid followed by digestion to liberate the small insert. However I still run into the issue of purifying away the parent plasmid. I've seen a few protocols using FPLC and/or size exclusion but I'm not sure how effective this would be.

Anyone have any ideas?


texts: Is there an antagonistic association between Penicillium and Aspergillus?

texts:
Some Aspergillus species appear to like walnuts. My question concerns the association of Penicillium and Aspergillus. No sooner does Aspergillus colonize a walnut (or some other challenging carbon source) than Penicillium seems to move in, eventually killing the Aspergillus colony.

A totally unscientific guess is that Aspergillus is a good colonizer and Penicillium a good opportunist and that this is a common pattern with these two species. Is there any science in this direction? I do recall a sort of well-known picture from an old text in which Penicillium is shown more or less strangling a species of Aspergillus. I didn't think about it much at the time.

The image attached is not very incriminating but the theme is the same. Penicillium are the green hand-like structures strewn about the clover-like Aspergillus. Foot-cell of the latter cropped.

This seems like a simple question but a quick search doesn't reveal a lot, I think in part because this would generally come up as a contamination issue.


texts: Can viruses stabilize and increase the shelf life of wine and other foods?

texts:
When you make wine, you use the yeast Saccharomyces cerevisiae to ferment sugary juices. After you're done, you want to avoid them doing anything by using some chemicals etc. There are also other living things (especially bacteria) that can ruin your wine or food during storage. For example, there are bacteria that would turn your wine into vinegar.

Have viruses been identified that infect and kill the bacteria that spoil wine or other foods?


texts: can genetic material actually provide a physical description of appearance?

texts:
A bodies genetic material provides the blueprint for your appearance. Your predisposition to be tall, freckled, blue eyed and blonde are encoded from birth.

However, external and environmental factors can influence the manner these instructions are carried out. For example malnutrition during childhood will affect bone and tooth growth. A lack of oxygen can lead to cerebral palsy with dramatic affects on the bodies muscle development (amongst other things).

Does your current genetic material indicate how you physically appear in real life and not just the genetic markers or 'potential'?

eg, if a scientist had a bloodsample taken today, I know they could say that the subject has obesity markers but could they actually say how fat the person was. Could they determine the difference between what the markers say and what the subject actually appears like?

Is current research limited but indicating that this might be possible in the future?


texts: Which complexes physically pump protons in photosynthesis?

texts:
The cytochrome b6f complex is often drawn as pumping protons, but then someone told me that actually there is no pumping, rather the Q cycle.

According to this view, what actually moves the protons is that a PQ takes up 2 H+ from the stroma as it is reduced and another two PQ release 2H+ into the lumen as they reduce PC and partially reduce the first PQ. The complex, therefore, does not physically pump the protons.

I now wonder if any of the photosynthetic complexes pump protons. For example, the PSII complex has PQ reduction with 2H+ removed from the stroma and its oxygen evolving complex releases O2 and 4H+ into the thylakoid lumen, so this could be its ‘pumping’ contribution.


texts: Experimental methods to demonstrate coupling of GPCRs

texts: How would you experimentally demonstrate receptor coupling through each of the G proteins, Gs and/or Gi?


texts:
While researching the F12 cell culture medium (Ham, 1965), I came across the term "essentially diploid Chinese hamster ovary cells". The terms "subdiploid" and "near diploid" were also used to refer to the same cells.

Attempts at searching Google Scholar and regular Google failed to turn up a definition of the phrase.

What exactly is meant by "essentially diploid", and how is it different from regular diploid cells?


texts: Since DNA footprinting is an old method I thought there may be some more recent and effective methods to identify a DNA sequence, do you know any of them?


texts:
Hair is mostly made out of keratin (the same stuff as fingernails and reptile scales). Hair "stubbles" left over from shaving are prickly.

Intuitively, growing hair should hurt. Dozens of keratin cactus-needles forcing their way out.

Does the hair somehow manage to avoid all the pain nerves?


texts:
I was pondering the question "Why do humans make music?" and on an intuitive level, my answer was "because of the feelings it evokes of course!"

But I then wondered, what about songbirds? Does a songbird have a feeling that compels it to make songs? I know there are plenty of instances of birds dancing and singing (at least, some call it that), but what motives does a songbird have to make birdsong?  How does this compare to the emotions and motives humans feel?


texts: Could someone explain why mold on my quinces grows in well separated circles around a center? To make clear, what I mean I post the picture


texts: How does plant life obey the constraint that the change in Gibbs free energy in a reaction must be negative?

texts: My understanding is that if a reaction takes place, either entropy of the system must rise, or energy must be released from the system as heat, or both. (Citation: paraphrasing from The Vital Question, by Nick Lane). But plant life seems to both decrease entropy, and absorb (not release) energy from its surroundings, by way of photosynthesis. How is this adhering to the constraint that the change in Gibbs free energy in a reaction must be negative?


texts: Minimum amount of RNA for cDNA conversion and qPCR

texts:
I searched several protocols for reverse transcription of RNA and all suggest using RNA concentrations of 1ug. Could a lower amount result in inferior transcript representation and therefore decreased quality of the qPCR results?

We use the SensiFAST SYBR Lo-ROX kit from BIOLINE. I was thinking of using 500ng instead of the suggested 1000ng. In order to accommodate the protocol, I would use 0.5ul of RTase to maintain the 1:1 (m/v) ratio. Buffer, DNase, water, and RTmix concentrations for the reaction I would keep the same. For the final dilution of the cDNA, I would dilute 5x instead of 10x to maintain equal concentrations.

Does anyone have experience with this? Does transcript representation suffer?
Do the suggested protocol adaptations seem reasonable?

Thanks for the help in advance.


texts: Im struggling to see how these are presynaptic terminals/knobs and not post synaptic

texts: How are these presynaptic terminals ? The action potential is generated at the axon hillock and moves down the axon (in this case to the right) , then at the end of the axon should be axon terminals and presynaptic knobs. Shouldn't the dendrites shown here have post synaptic knobs with receptors for the neurotransmitters ?


texts:
I have trouble in solving this exercise.

Exercise

  A circular plasmid of 10,000 base pairs (bp) is digested with two restriction enzymes,A and B, to produce a 3000 bp and a 2000 bp bands when visualised on an agarose gel. when digested with one enzyme at a time, only one band is visible at 5000 bp. If the first site for enzyme A(A1) is present at the 100th base, the order in which the remaining sites (A2,B1 and B2) are present is?

Why I struggle with this exercise

How can a 10,000bp plasmid produce 3000bp and 2000bp only on agarose gel. I mean where are the remaining 5000bp? I dont know if my concept is right.

Linearised bands on an agarose gel may be doublet. That can clear the doubts in problem. But still I dont know how to do a reasonable restriction mapping and find out sites of different enzymes.


texts: How can you develop a bacterial infection when taking antibiotics for another area of the body with a bacterial infection?

texts:
How can you develop a bacterial infection when taking antibiotics for another area?
For example, "if someone was prescribed an antibiotic for a bacterial infection of the throat and while taking the antibiotic tablets they developed a bacterial infection in their toe.  Explain why the antibiotics taken for the throat did not prevent the growth of the bacteria in the toe".
Is it because the bacteria in the toe is a different type and didn't respond to the bacteria developing the toe (don't think so, but not sure), or
was It because antibiotics don't prevent the development of bacteria they only inhibit it once grown and kill it, or
something else?


texts: I'm just getting interested in genetic structure and I decided to find a FASTA formatted genome (human) and I found one here. However, I'm confused. I know that A can only match up to T and C to G but it appears as though T is matching up to T, A to A, C to A, and etc. How is this possible? Can there be gaps where T,A ,C ,or G is connected to nothing? Small part of genome: ATTTAGAAATGACTAACAATTATGTAGGTTTATTTCTCTCAGTATAGAATGTTCATATAGAATT


texts: The position of the macula in comparison to the blind spot

texts: Which is located in a higher postion? Macula or blind spot?


texts: What is the counter-reponse to a sound stimulus?

texts:
I am slightly confused on finding out what is the counter-response because of a stimulus.

For example, if we hear a sound, I believe the sound waves are the stimuli? So is the counter-response the vibration of our eardrum or the sensation of hearing the sound?


texts: Are there any other animals that become attached to a non-living object?

texts: Do any animals become psychologically attached to any non-living object that is not useful to the animal for any of its physical needs, like some children do to stuffed animals? Some children are so attached to their toys that they take them with them whenever possible, and are upset when the toy goes missing or is taken by another.


texts: Does DNA have a phosphate group or phosphoric acid?

texts: I am confused about the structure of nucleotide of a DNA. I have seen that it has a phosphate group(PO₄³⁻) in some books but phosphoric acid(H₃PO₄) in other ones. Which one is right?


texts: Do other animals suffer from myopia or hypermetropia?

texts: Mammals have eyes similar to humas and many other animals like octopuses have a lens in the eye. So do they have such eye defects? If yes, how do they overcome it? Do they feel selection pressure against them in such cases?


texts: Why do people say that smallpox has been eradicated?

texts: I keep reading things like “smallpox has been eradicated” or “there are only two samples of the virus left in existence in a lab somewhere”, but couldn’t there be a bunch of smallpox viruses in an alleyway where some infected person sneezed years ago? Is there some reason the virus can’t exist without a human host?


texts:
Three proteins A, B and C of equal molecular weight are being investigated in a study. They contain six, four and four cysteine residues respectively. Only Proteins A and B were treated with β-mercaptoethanol (which reduces disulphide bond) and heated in boiling water bath for a few minutes. Which of the following is expected in the SDS PAGE gel run?

a. Protein C will move fastest.

b. Protein B will move fastest.

c. Proteins A and B will move at the same speed but faster than C.

d. Proteins B and C will move at the same speed.

Before knowing the answer the I thought the answer would be b. Because as Protein A has the most no. of amino acids so it will be behind Protein B and C for sure. And for protein B and C, as Protein B has been in a reducing environment it will not form disulfide bridges but Protein C will, so it will be billore and hence will be behind Protein B. So B will be fastest?

But the answer key says C, I am not really sure how?

So the answer is C . Before knowing the answer I thought the answer would be b. Because as Protein A has the most no. of amino acids so it will be behind Protein B and C for sure. And for protein b and c as Protein B has been in a reducing environment it will not form disulfide bridges but Protein C will so it will be billore and hence will be behind Protein B. So B will be fastest? But the answer key says C


texts: When assessing a threat, does the amygdala compare the stimulus to memories of the amygdala or the hippocampus?

texts:
Two excerpts from the one article.
My understanding of this excerpt is that the amygdala is using its own memories:

The amygdala learns how to respond to various stimuli based on it’s reference to implicit memory and makes decisions on how to initiate an emotional reaction to such stimuli. The emotional memory learned and utilised by the amygdala is implicit or unconscious and is in contrast with explicit (declarative) memory that is processed by the hippocampus.

My understanding of this excerpt is that the amygdala is using the memories of the hippocampus:

Incoming information goes to the thalamus and then directly to the amygdala while another slower path goes to the neocortex. If the amygdala perceives the record of experiences in the hippocampus matches incoming information, and the amygdala judges that the stimuli is a fight, flight or freeze situation

Source: https://www.thescienceofpsychotherapy.com/the-amygdala/


texts:
I have the following exercise to solve:

To be honest, for both parts, my only idea so far would be to divide the rate expression by the sphere area and multiply by the new available areas (that of a circle for part a and that of many circles for part b). But if I do this, I will have an "a" parameter always, which makes no sense because it is representative only of the sphere.
Any ideas on how to approach this?
All help is greatly appreciated.


texts: How does cholesterol affect the fluidity of a plasma membrane?

texts:
I was previously taught that cholesterol affects the fluidity of a plasma membrane. At high temperatures, cholesterol decreases fluidity and at low temperatures cholesterol increases fluidity. The Khan academy and Wikipedia pages below say the same thing.

https://www.khanacademy.org/video/cell-membrane-fluidity
 https://www.wikiwand.com/en/Membrane_fluidity

Yet, in a current college course, the textbook ("Molecular Biology of the Cell 6th" by Bruce Alberts et al.) says that cholesterol reduces the mobility of the first few CH2 groups of a phospholipid's two fatty acid chains. In this way, the cholesterol makes the lipid bilayer more rigid and decreases the lipid bilayer's permeability to small, water-soluble molecules. However, it says that cholestrol does not actually make the membrane less fluid.

Is the textbook from my current course just a more nuanced explanation, or have I misunderstood something else?


texts: Why do cells need all the genes of all the 22 pairs (excluding the 2 X- or Y-chromosomes) of autosomes in every somatic cell, when each and every cell which is specialised for its function does not manifest all the phenotypes that are encoded by the genes present? Aren't the genes other than those whose phenotypes (& hence some chromosomes) are expressed by that cell, redundant?


texts:
I saw a mammal that looked like a large squirrel. I haven't seen anything quite like it. Can you help me identify it?

Squirrel-like, "hunched over" posture.
It was too large to be an eastern squirrel—approximately 2.5 feet, from nose to tail.
It had a fluffy tail like an eastern squirrel, not short and rat-like like a ferret.
Black face with white nose, body was chestnut-brown.
I saw this on the ground, not in a tree.
I saw it in a pine forest in east-central Alabama.
At one point, it sat up on its hind legs.


texts: Do all gene mutations in pathogens lead to more harmful consequences for humans?

texts: It seems that the concern we always hear is that bacteria and viruses mutate to dodge our treatments either through random mutations or survival of the fittest. Do harmful living things ever mutate to become not harmful?


texts: Is the General Cirrate Octopus Form the Basalmost Octopoda Morphology?

texts:
The reason I ask this is due to the distinctive internal mantle shells of cirrina, of which the incerrata have stylets that are a remnant of the cirrate shell. Along with this, both cirrate octopuses and Vampyroteuthis have a gladius (although with different morphologies) with fins upon their mantles, which incirrate octopuses lack.
Also, a relatively recent study presents a view that cirrate octopuses are actually paraphyletic, being an evolutionary grade rather than a monophyletic group. Can it be inferred then that the basalmost octopus form is then a pelagic form with a gladius that uses mantle fins as the primary form of locomotion, and the incirrate form normally associated with octopuses is a drastic deviation?


texts: Algal booms low phosphate and nitrate levels in Polluted water?

texts: Why does eutrophication (algal booms) take place in polluted water with low phosphate (1mgL-1) and nitrate (0.8mgL -1) concentration?


texts: Do viruses suffer from Muller's ratchet?  Can it significantly influence the current coronavirus pandemic?


texts: Cold adaptation in proteins, at sequence & structural level

texts:
When looking for cold adaptation in unicellular eukaryotes there is not much work found. Most of the time general sequence comparative sequence analysis between marine mesophile & psychrophile also does not give clear results. If I am planning to study at structural level (homology modeling) will I get answers? What type of parameters can I look to study? Which proteins are expected to provide cold adaptation apart from ice binding or antifreeze proteins because IBP & AFP cant be found by sequence comparison. Is it possible to give some ideas regarding this?

Thanks


texts:
Sources include any exporting organs, typically mature leaves, that
  are capable of producing photosynthete in excess of their own needs.

  Sinks include any nonphotosynthetic organs of the plant and organs
  that do not produce enough photosynthetic products to support their
  own growth or storage needs. Roots, tubers, developing fruits, and
  immature leaves, which must import carbohydrate for normal
  development, are all examples of sink tissues.

Sinks are always supplied by sources. Now, I want to know do all sources transport their photosythetic to all parts of plant or some sources just supply some especial sinks.

This is a question for me:

Do all sources supply all sinks on a plant?


texts: I have heard about human anti-mouse antibodies (HAMAs) and read that HAMAs neutralize murine antibodies, therefore decreasing the effectiveness of those murine antibodies. Is this true that HAMAs neutralize the murine antibodies? How?


texts: Has anyone attempted to add extra senses to a creature through a BCI/Neural interface?

texts:
Basic BCI's (Brain computer interfaces) have been available for quite a while now and allow users to preform rudimentary tasks such as moving prosthetic limbs with force-feedback or moving a mouse on a screen through only neural impulses.

I'm interested if anyone has performed experiments in the direction of adding non-native extra senses to a creature using a neural interface/BCI. For example, feeding a magnetometer's sensor reading or clock data into a BCI and using that to give the person/creature a "sense" of magnetic fields or exact time.


texts: Why don't the apples seeds from grafted trees produce the same kind of apples?

texts:
As Wikipedia says:

Grafting is a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together.
In most cases, one plant is selected for its roots and this is called the stock or rootstock. The other plant is selected for its stems, leaves, flowers, or fruits and is called the scion or cion. The scion contains the desired genes to be duplicated in future production by the stock/scion plant.

So why I don't get the apple-tree of the scion kind if I plant the seeds from an apple which has grown on such a tree? I would expect that the genes in the apple seeds must be the same. However if I plant the seeds, I have to graft the new seedling again.


texts: How many sensory neurons are in the human body?

texts:
While I understand that there is a wide disparity of precision when it comes to specifying what constitutes "sensory neurons/receptors", I'm trying to find an authoritative source to provide at least a rough order of magnitude estimate on the number of receptors in the human peripheral nervous system (including skin, tongue, eyes, ears; but also mechanoreceptors and proprioceptors as well). The only sources I have found so far (here and here) only provide hints at the answer. I have found estimates as high as 15 billion, and as low as 3,000,000, but none of these guesses cite authoritative sources.
As I'm sure you can tell, I am not a student of anatomy (my interests lie in cognitive science and artificial neural networks), so forgive me if my question is too imprecise.  But to put it simplistically: what I want to know is, roughly how many externally-produced sensory signals (channels) does the human brain have the capacity to process? Again, I am not looking for a precise answer, but I'm hoping to at least reduce the uncertainty to less than four orders of magnitude.

CONTEXT: My purpose in this investigation is to try to quantify the magnitude of the computational capability of the brain with regard to processing external signals. If one were to imagine an "artificial nervous system" (as distinct from an artificial neural network), how many input sensors would it be able to simultaneously process if it were on par with a human brain?

UPDATE: I recognize from the comments the inherent ambiguity of my question, so let me attempt to clarify. Assuming that the number of incoming signals to the brain at any one time is limited by the number of neural connections between the brain stem and the spinal column*, can someone provide an indication of what that number might be.
* (if that assumption is overly simplistic, feel free to enlighten me)


texts: Why does fever above 102 herald a cancer patient's death?

texts:
I was recently intrigued by a longtime hospice nurse's observation that her cancer patients die a different death than her Alzheimer's, multiple sclerosis, heart failure and COPD patients.

She stated that the cancer patients will typically develop a fever over 102 degrees during the last 48-72 hours of their life, something that is not normally seen in her non-cancer patients.

Any ideas on the underlying biologic reasons for this extinction burst phenomenon and how might this be related to the high fevers induced with Coley's Toxins?


texts: Why might food go bad in an oxygen-free environment?

texts:
I was recently watching a video from the International Space Station (Making a peanut butter sandwich in space), and I noticed he mentioned that a tortilla kept in an oxygen-free environment could last up to 18 months. Impressive, but it got me thinking: Why would some foods ever spoil if kept in a state where molds would not be able to grow? Would it be that other micro-organisms in things like the moisture present in the food eventually take their natural toll? Just a curious thought I had while watching through these awesome ISS videos.

Thanks for any answers!


texts: Did the old world have relatives of plants which were brought after the discovery of Americas?

texts: When the Americas were discovered many plants were brought back to Europe. For example: potato, tomato, strawberries, chilies etc. At the same time many animals were brought to the Americas including: horses, cattle, sheep, and camels. It seems from the records that there were relatives of these animals in the Americas — for example llamas are in the same family (Camelidae) as camels. I wonder if there were relatives of these vegetables from the Americas already present in Europe or anywhere else in the old world.


texts: How to relate human metabolic model reactions and cancer drug targets / reactome items?

texts:
Trying to find a way to take a cancer drug (from CancerDR, for instance) and infer the metabolic reactions that are affected by it in the Human Metabolic Model.

Essentially, I would like to know which HMM reactions are affected by a certain cancer therapy drug, especially the ones found in the Cancer Cell Line Encyclopedia.

Example:

Searching for the reactions that are associated with the HSP90 protein, which is targeted (to some extent) by the 17-AAG agent.  That way, I can trace back the relevant section of the HMM and mark it as 'affected' by that agent.

This could be a very broad or naïve question, but I am afraid I don't know enough to be able to determine that.

If someone can only provide some tip or guidance, that will be greatly appreciated as well.

Thanks very much!


texts: What is the genome size of Saffron (Crocus sativus)?

texts: I searched the web but cannot find an answer for my question. Has the genome size of Crocus sativus been determined?


texts: How much vitamin C has a noticeable effect on E.coli k12

texts:
I am doing a research on effects of different concentrations of vitamin C on serial dilutions of E.coli k12. I am looking for literature that has already shown effects of vitamin C on E.coli, but there is a vast amount out there (26 thousand Scholar hits).

What might be the main effect of Vitamin C on E.coli? Is 1000mg vitamin C enough to have noticeable effects on the bacteria?


texts: I am not sure whether the word "touch sensitive" is precise enough. What I am looking for is a list of plants that respond to touch noticably  like Mimosa Pudica. I only know of Mimosa Pudica example. Is there any other such plant?


texts: Can DNA fingerprinting tell you if someone has been genetically engineered?

texts:
I am writing a fictional novel about an extensively genetically engineered man, unbeknownst to him, who gets into trouble on a regular basis. The man is physically large and strong, very fast (tiger-like hand speed), and he has exceptional sensibilities such as night vision, hearing and smell. The FBI gets some of his saliva from a crime scene and creates a DNA fingerprint from it.

My question/s is: could the technicians/scientists who perform the DNA fingerprinting procedure for the FBI be able to tell that this man is different from other humans? Would it be possible for someone to be human and have a different number of chromosomes? Does all DNA fingerprinting appear as bar codes and mean nothing until compared to a sample?

Please forgive my ignorance on the subject. Thank you for any input.

Chris


texts: Are there any bacteria, virus or mold that can withstand ozone?

texts:
Ozonation is often promoted as one of the most effective disinfection procedures. There are numerous reports on how ozone effectively kills bacteria and molds, and disarms viruses within seconds due to its exceptional oxidative activity and small size.

Still, there are examples of thermophilic bacteria existing in volcanoes, as well as viruses in arctic ice, so they both can adapt to extreme conditions. Are there any examples of bacteria, viruses or molds (not necessarily pathogens) that cannot be killed by ozone, or at least show significantly higher resistance to oxidation?


texts:
I'm trying to understanding base pairing. So every linear chromosome is a double stranded double helix. Is this double stranded property the same as saying an organism is diploid? Or do the chromosomes of a haploid eukaryotic organism, like a member of Fungi, each have 2 strands (with the purines always pairing w/ pyrimidines), which would imply that diploids organisms actually have 4 strands?

EDIT: Part of my confusion comes from the fact that in diploid organisms, each parent gives 1 chromosome to the child. If the double stranded property is the same as saying an organism is diploid, does this mean that say if a nucleotide on one chromosome is A, then the nucleotide on the other chromosome in the same loci must be T? Doesn't chromosome mean a paired up strand, not a single strand?


texts: Is it possible to calculate the evolutionary response to nonlinear selection gradient as a change in variance of phenotypes?

texts:
I often see the breeders equation written like this:

$R = h^2s = \frac{V_a}{V_z}s = V_a\beta$ or $\Delta \bar z  = G\beta$

But is it possible to get something like this:

$\Delta \sigma_z  = G\gamma$

In this case, it would be the change in variance of the population due to nonlinear selection.

Basically, it would me that the response of selection is a direct measurement of the change in $V_z$. So to come back to this equation: $R = \frac{V_a}{V_z}s$, it would mean that $\gamma$ is related to $V_z$ somehow. But is there a way to predict what would be the response?

Is it possible to also predict the total response of a non-linear selection gradient if there are multiple traits?

When one wants to calculate the total response to selection, it is needed to account for the correlated effect of selection on other traits (correlational selection):
$R_1 = V_{a,1} *z_1 +\text{COV}_{V_{a,12}} * z_2$

$R_2 = \text{COV}_{V_{a,21}} * z_1 +V_{a,2}* z_2$

In matrix form:

$
\begin{bmatrix}
    R_{1}    \\
    R_{2}
\end{bmatrix}
=
\begin{bmatrix}
    V_{a,1}       & \text{COV}_{V_{a,12}} \\
    \text{COV}_{V_{a,21}}       & V_{a,2}
\end{bmatrix}
* \begin{bmatrix}
    \beta_{1}    \\
    \beta_{2}
\end{bmatrix}
= \boldsymbol{R}=\boldsymbol{G} \boldsymbol{\beta} $

How would that be translated to non-linear selection?

EDIT:

I think this answer is here:

$\Delta \sigma_a^2 = \frac{\sigma_a^4}{2}(\gamma - \beta ^2 )$

But this equation predict a change in genetic additive variance not phenotypic variance. Would it be possible to simply take $h^2=\frac{V_a}{V_z}=\frac{\sigma_a^2}{\sigma_z^2}$ and get the change for phenotypic variance?

This could also represent an answer:

$\boldsymbol{G}^* -\boldsymbol{G}=\boldsymbol{G}(\boldsymbol{\gamma}-\boldsymbol{\beta}\boldsymbol{\beta}^T)\boldsymbol{G}$


texts: Is it true to say that the more an organism is smaller, the faster it's going through evolution?

texts:
As someone who never formally learned biology, I assume that currently;

The number of species of (non Archaea) Bacteria
The number of species of Algae
The number of species of Plankton
The number of species of Bivalvia
The number of species of Poaceae
The number of species of flowers
The number of species of mushrooms
and of many other sets of species

Are all vast (from hundreds to tens)

Is it true to say that the more an organism is smaller, the faster it's going through evolution (hence, is generally more genetically varied)?


texts:
Tendon injuries are notoriously slow to heal for humans, and quite often do not heal properly due to a variety of reasons. Do any animal have a tendon repair process that is more efficient than in humans? Efficient = faster + higher repair quality. If so, what property(ies) make the  tendon repair process more efficient?

I unsuccessfully searched for "tendon repair in animals" on Google and Google Scholar.


texts: Is the ratio Brain Mass/Total Mass still considered a valid indicator of intelligence?

texts:
I was reading this(1) and it led me back to ask a very basic question (I'm not a neuroscientist).  All the way back to undergrad anthropology and neuroscience courses I remember being taught the general rule of relative intelligence was that one looked at the ratio of the brain mass over the total mass of the animal (or the estimations therein from let's say fossils).

I know a lot of the interesting neuroscience research going on these days does looks into bird brains, particularly within Corvidae.  It would seem that birds are often much more efficient in the abilities they seem to show with considerably less brain mass.  I do realize that birds often weigh very little as well, so perhaps the ratio is preserved?

I also realize that within birds, they see better ratios in more intelligent birds.  But what about the comparison from mammals to birds?

Dinosaurs are often predicted to not be intelligent because of the enormous body size and small cavities for a brain.  Now I realize that some dinosaurs were actually quite tiny, but this is just an example.

Given birds' close genetic link to dinosaurs, could it simply be that they were just doing more with less?  The mammalian brain is a huge caloric burden, so perhaps this would show an efficiency that could be selected for?

Thus as the title suggests, my main question:

Is the ratio of brain mass to body mass still considered to be a valid indication of intelligence of a species in modern (current) neuroscience?  Certainly there are exceptions, but is it still considered the rule of thumb?

EDIT: I also wanted to point out the first article(2) I started to read after formulating the question.  It made me question the usefulness of encephalization in addressing this issue at all, but I don't/didn't feel adequately trained to evaluate the conclusions of the meta study.

Again, this still leaves us comparing within primates, which still leaves me feeling that Corvidae have some really impressive efficiency going on with their overall brain mass.  Which then leads to hope that some dinosaurs could be at least equally intelligent, if not more so (noted that this is complete conjecture).

(1) Front Hum Neurosci. 2013 Jun 6;7:245. doi:10.3389/fnhum.2013.00245. Print 2013.

(2) Brain Behav Evol. 2007;70(2):115-24. Epub 2007 May 18.


texts:
I found this bug skin on my friend’s couch. Is it a bed bug? Could it be any other bug?

Here is a photo.


texts: Is once per day the optimal sleep pattern for all mammals?

texts:
If a typical human body clock is 8 hours sleep, 16 hours awake, interested to know if any mammals have:

a 12 hour body clock (4 hours sleep, 8 hours awake)
a 6 hour body clock (2 hours sleep, 4 hours awake)

And very interested to know if any mammals' sleep patterns are on an "as-needed" basis - i.e. simply sleeping whenever tired, without ever establishing any particular pattern over the days/weeks


texts: What's the relationship between snail movement and rain?

texts: I have a question about the relationship between snail and rain. A few days ago I found snail shells in a moist area and I brought them in for crafts work (I thought they were empty because snail usually come out if you poke them). After a few days it rained, and I found that the snails have moved from the space i put them in (but not far). My question is why did they move after it rained  outside but not when I brought them in a week before?


texts: What is the most frequently occurring health problem of rodents caused by the usage of pesticides on the agricultural fields in the United States?

texts: For centuries the mankind has used pesticides to protect its crops but within the last century the pesticides have become more artificial and toxic. It is a well known fact that most of the pesticides can have fatal consequences, when one consumes them to much, as different studies have shown links between the pesticides and different diseases like cancer, ADHD and also different birth defects. People today are more aware about it and try to eat more organic food, but the pesticides are still in constant use and therefore it is still a threat to animals, who are in direct contact with the pesticides.


texts:
I did some normal google.book search and found the two importance of fate maps-

1. They helped establish the idea that communication between different parts of an embryo leads to the formation of new cell types and have thus helped discover different signalling pathways.

  2. They enable us to interpret experiments in which cells of the embryo are exposed to conditions that may alter their developmental fate.

I really don't know where to look for the experiments that support these merits of fate maps. So is my question,what are some experiments that support these merits?


texts:
I have a question regarding how molecular interactions manifest in physical actions - such as hanging from a bar. To the best of my understanding, when it comes to the contraction of muscles, ATP is required for myosin to detach from actin - terminating contraction.

So, what I'm wondering is when we are hanging from our bar, utilizing our grip strength, we are in a constant state of contraction. However, eventually, our muscles fatigue and we let go. I presume this is because we are running out of energy, but isn't energy (ATP) what was necessary to terminate contraction? Why do we eventually let go of the bar and how is this represented on the scale of muscle fibres?


texts:
As I was studying for my GRE exam, I was reading on Mitochondria. I then remembered that they undergo replication similar to bacteria. So I googled for info and found on Wikipedia that there is a " near-absence of genetic recombination in mitochondrial DNA"
https://en.wikipedia.org/wiki/Mitochondrion#Replication_and_inheritance

So then, if there is a lack of genetic diversity, how can these mitochondria still be functional? If we assume they are affected by random mutations as DNA can be. Is it the case that they replicate infrequently enough to not suffer ill-effects of low diversity?


texts: Many protocols in my lab use sorbitol in buffers.  For instance, in co-immunoprecipitation, we include it at a final concentration of 200 mM in our lysis buffer. I'm not entirely sure why though.  I believe it might be as a crowding agent. But even if this is the reason, I'm not entirely sure what this means.  Could someone explain?


texts:
I was under impression that data about quite a lot different species using different tools is a fairly modern phenomenon, i.e., all of the research is fairly recent.

Around 50 years ago it was widely believed, by scientists too, that it was only apes that are able to use tools. I was recently told that it's basically nonsense and scientists have been studying different tool-using animals since the beginning of the 20th century or earlier.

Where could I get more info on research done in this area? I'd be especially thankful for those done in USSR, since it used to be my country and my knowledge on everything was basically limited by the Iron Curtain. However, I am also interested in research done worldwide as well.


texts: Do we use 100% of our cerebral capacity?

texts:
I saw a movie yesterday called Lucy. In this movie, a girl called Lucy absorbs a large amount of CPH4, and her brain capacity slowly increases.

So that brings me to my question which is :

Do we humans use 100% of our cerebral capacity or do we just use 15%?


texts:
I am using PCR to amplify a 1000bp region of the CytB mt gene. Some of the samples had not amplified and I wish to change the reaction components (or use additives like BSA) to attempt at getting amplification. The DNA was extracted from liver/muscle samples, so I am not expecting many inhibitors present, but I am eluting samples in AE  buffer.

I used the following combinations of PCR mixture but the reactions still failed (reaction volume 20ul)

Combination1 : MasterMix (10ul), Primer 1 (1ul), Primer 2 (1ul), BSA 2mg/ml (2ul), water (4ul), DNA (2ul)
Combination2 : MasterMix (10ul), Primer 1 (1ul), Primer 2 (1ul), BSA 2mg/ml (4ul), water (3ul), DNA (1ul) : Tried to increase BSA concentration and reduce DNA to decrease the volume of inhibitors (if any) going into the reaction mixture.

Someone who has previously used BSA to successfully troubleshoot PCRs, am I going about this in the right way ? If I need to take a different approach please help me out.

Thanks!


texts:
in studying maturation of lymphocytes into two different types-T LYMPHOCYTES and B LYMPHOCYTES. it is mentioned that if a lymphocyte matures in thymus gland it becomes T LYMPHOCYTE and becomes B LYMPHOCYTE if matures in bone marrow {bursa region}.

also HIV virus attacks helper t lymphocytes . I was thinking that if we could make the initial immature lymphocytes in thymus made outside in vitro  { like from stem cells or likewise from clone etc or some other alternatives} and then inject them in patient so as to overcome their deficiency .

is it possible?


texts: The information carried by nerve signals

texts: Action potentials carry nerve signals in individual neurons and somehow encode information. My question is if it is possible to read that information carried by the nerve signal and feed it into a computer to understand what information it contains?


texts: Can skin acclimatize to a the humidity level?

texts:
When the outdoor temperature is low, the absolute humidity is low because cold air holds less water. When the heat is turned up indoors the relative humidity decreases and during days with cold weather it can fall below 10%. This can lead to cracked skin or lips because, I assume, dry air draws more water from the skin. So my question is, can skin acclimatize? Around here in New York, some people get cracked knuckles every winter or use moisturizer to prevent them (I use nasal saline for nosebleed prevention). If those people lived in dry climates would they have this all year around? Or does the skin (and nose) eventually acclimatize?

If I install a large humidifier in my home could that actually have adverse effects by preventing me from acclimatizing (that is, making my nose less naturally lubricated), thereby possibly causing problems when I enter other houses or buildings?


texts: Are our ears more sensitive to low or high pitched sounds?

texts:
I am a Physics student who also love music and learned a little bit about Medical Physics. I know that the basilar membrane in the cochlear duct enables us to distinguish different frequencies. The different parts of the basilar membrane have different resonance frequencies and this leads to frequency dispersion.

I've also learned that the pitch of a tone is determined by the fundamental frequency, and the overtones just add timbre to the sound, and are difficult for common people to hear separately.

I think the above implies our ears are more sensitive to lower frequencies. However, this is obviously not true when we listen to a symphony, in which I think most people are more "sensitive" to the higher parts. And I think this is the reason while the melody is usually in the highest part in a song.

So I am confused. Are our ears more sensitive to high frequencies or lower frequencies? Is there a biological explanation of why we usually tend to hear the highest-pitch part of a piece of music?


texts:
Is there any known pharmaceutical or chemical that could cause infertility in humans in a single dose with few or no other effects?

The context is that a number of claims are circulating about vaccination being a "cover" for a plot to render males and/or females infertile. I claimed that it is unlikely that there is a known way to make a person infertile with a single dose of a chemical without significant side effects. However I couldn't find a source.

I'm asking as I believe it is important to have scientifically accurate responses to rumors and the like, even if they are outlandish.


texts: It is surprisingly hard to find information about the timing of neurons, in particular how long an action potential can contribute to the summation of a neuron. Is it on the order of milliseconds or rather seconds, i.e. for a neuron to fire, do many of the presynaptic neurons fire about at the same time?


texts: Why does the affinity of haemoglobin for oxygen decrease at high altitudes?

texts:
My class 12 NCERT book says, Pg 226

  The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of haemoglobin and by increasing breathing rate.

Why should the haemoglobin binding capacity decrease at high altitude?

I think it should increase for better oxygen transfer and uptake from air. The concentrtion of oxygen in the atmosphere decreases with height. Hence, if the haemoglobin binding increases, we will be able to draw more oxygen from the air and transport it to the cells.


texts:
I suppose what prompts me to ask this question is my wondering if it is possible to have a multicellular prokaryotic organism. For instance, can a biofilm be considered a single organism? Why or why not?

Why is it that multicellular prokaryotes do not exist (if they do not)?

At what point can a collection of cells be considered one whole -- do they need to all share identical DNA?

Fire away.


texts: Are quaternary protein monomers unique to a particular protein complex?

texts:
I know that quaternary protein structures are formed exclusively via non-covalent bonds. My biochemistry professor discussed a viral capsid that is essentially one quaternary structure with 240 individual monomers of 4 kinds. I suspect that for this protein coat to be stable, the non-covalent bonds holding it together must be rather stable. He also mentioned that different monomers can join to form the functional protein complex from relatively far distances, like across an entire cell, which once again leads me to believe that both monomers must be interacting with each other very strongly.

My question is: Since a strong non-covalent interaction is required between (at least) two protein monomers to form the functional quaternary structure, can one particular protein be a monomer to an array of different quaternary complexes? Are there any examples of this?


texts: Which Enzymes are Responsible for the Biodegradation of Noladin Ether?

texts: Which enzymes degrade the CB1-specific endogenous cannabinoid 2-arachidonyl glyceryl ether? (Noladin ether)


texts: How to use mechanical microstrainer to extract tissue proteins from human?

texts:
Background:

There are many methods to extract proteins form human tissues out there. The majority of them use an extraction buffer containing variable concentrations of detergents and protease inhibitors to preserve the extracted proteins as much as possible and keep them functional until being analyzed by downstream applications, like western blot, ELISA, etc. One drawback of this chemical extraction is the interaction of the buffer components with antigen-antibody binding in the analysis. The interaction is sometimes difficult to predict, therefore, validation of the sample matrix is necessary before going into the real analysis, e.g., for ELISA, spike-and-recovery, linearity-of-dilution are two known validation assays to this effect. For more info about these two assay you may find this answer useful.
One optimal way would be to avoid such interaction by avoiding the use of extraction buffer altogether and using mechanical methods plus protease inhibitors, instead. I don't know the drawback of this method, but one may be it is not as effective to get cytokines out their vesicles to be accessible by assay analysis.

Questions:

How to use Microstrainer as a mechanical substitute for protein extraction in human gastric tissue?
What are the pros and cons of using the Microstrainer?
How effective is it to measure human cytokines from tissues?


texts: Why does heating kidney beans at a low temperature potentiate the toxicity of phytohaemagglutinin?

texts:
I recently found out that red kidney beans contain a relatively high amount of the toxic lectin, phytohaemagglutinin.
An article on phytohaemagglutinin on the FDA website states:

Several outbreaks have been associated with "slow cookers" or crock pots, or in casseroles which had not reached a high enough internal temperature to destroy the glycoprotein lectin.
It has been shown that heating to 80°C may potentiate the toxicity five-fold, so that these beans are more toxic than if eaten raw.

What I do not understand is how the toxicity could increase if the beans are cooked at lower temperatures in a crock pot. I would understand if the toxicity remained the same (that is, not be deactivated), but I thought a toxin is nonliving (i.e., unable to grow and reproduce) since it is not a bacteria?
I know nothing about biology, so I am utterly confused.


texts: Terminology for quantitative response of T cells to antigen complexes

texts:
In the article, there is a statement which is:

  Although DCs are
  remarkably efficient in evoking T cell responses with few antigen–
  MHC complexes (1–100 per DC) (1–3), they must first
  encounter a T cell with appropriate antigen specificity (one in
  105 to 106).

What does the part  "Although DCs are remarkably efficient in evoking T cell responses with few antigen– MHC complexes (1–100 per DC) (1–3)" mean?
What is the significance of the value "1–100 per DC"?
What does evoking T cell responses with few antigen–MHC complexes mean?


texts: Does posture matter while drinking water?

texts:
I have heard a lot of people (where I am from, India) say that one must drink water sitting, not standing. Recently, I also came across a video that said the same thing (link). The reason given is that when you drink water standing, it goes to the colon too quickly, whereas while sitting, the water is better absorbed by the organs. Is this true? Is there a biological basis for why I should drink water sitting?

I tried to find literature on this matter, but apparently there isn't a whole lot. I found this paper where they tried to see the water passage rate in the GI tract of rabbits, mentioning how the water goes from stomach to cecum to proximal large colon, but obviously did not study posture.

Note: I think this question belongs here better than Skeptics.SE as I am looking for a biological explanation


texts: Where can I find a global life expectancy table?

texts: I've found good information on specific countries and demographics, but I can't seem to find global numbers.  I know that the world life expectancy is around 71.0, but I'm trying to get a percentile breakdown in the form of something like an actuarial life table.


texts: I found groups of these growing in the Lassen National Forest (Susanville, CA, USA). It looks like some sort of mushroom. I have Googled extensively, but can't seem to find a match.


texts: What is the relationship between the light and dark reactions of photosynthesis?

texts:
My main concern is why are the dark reactions (those that produce hexose) needed? As far as I understand, the sole purpose of photosynthesis is to synthesize carbohydrates, which are only used for energy storage. So, why don’t plants store energy directly as ATP (by photophosphorylation) and not as carbohydrates? (Of course, that would be too bad for other creatures.)

Elaborating my question:

Plants use chlorophyll to convert light energy into chemical energy of ATP and NADPH by photophosphorylation and chemiosmosis.
Then plants use the ATP and NADPH to synthesize glucose by the Calvin cycle.

So, what is the need of step 2? Why don‘t plants just use that ATP and NADPH for their metabolism?

PS: although @David has provided a nice answer to the current form of the question, the selected answer by @christian still remains selected since it answered my original query i.e. why excess ATP is not feasible for plants instead of why synthesis of carbohydrates is important. Any further answers/comments shall address the latter one, although none of them can be selected as correct since the latter query is not the original one.


texts: What is in the space between neurons in a brain?

texts:
When neuron animations are displayed, there are frequently seen neurons, axons arranged in a lattice with a lot of empty space between. I'm interested if there is indeed empty space in the brain, or if it is filled with some sort of fluid? I've checked an article on cerebrospinal fluid but am not sure that it is present all throughout the brain.

The reason I'm asking is that I'm thinking of neurotransmitters- they are released in synapses, but I'm not sure how they stay there - are they suspended in some liquid as well?


texts: Has anyone 'broken' an organism and then restored it to life?

texts:
Has anyone 'broken' an organism, rendering it unable to reproduce, then repaired it and observed it returned to being able to reproduce?

An example would be to restore the reproductive capacity to a cell rendered lifeless from radiation.

I've attempted, several times over many years, to find any information about this and all I've found is abiogenesis and the Miller-Urey experiment which is not the question at hand.

If there is another technical term referring to repair of life, versus creation, then I am unaware of it.

ADDENDUM: Clarified question ...limited to reproduction vs. living.


texts: My parents have B +ve blood group in fact my brother also have B +ve blood group, then why my blood group is O -ve ?


texts: What will happen if a foetus is Rh- and the mother is Rh+?

texts: If a mother has Rh-negative blood and her foetus has Rh-positive blood it will result in rhesus incompatibility and lead to erythroblastosis fetalis. What will happen if the reverse occurs, when a mother is Rh+ and the foetus is Rh-?


texts:
Why do denatured proteins tend to be less soluble than the native protein?
In terms of hydrophobic effects, could anyone explain this phenomenon for me?


texts: If calcium ions and cholesterols are found on the surface of the skin, would it be possible for Vitamin D to be synthesised on the skin?

texts: Calcium ions are abundantly found in the extracellular space of the stratum corneum area, the top most layer of the skin (Skin Barrier and Calcium; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5929942/). Isn't it very probable that it can also be found on the surface? Calcium ions are also actively involved in regulating the water gradient of the stratum cornuem. However, they may be easily washed off from the surface of the skin through the regular use of water and surfactants. Plus, the use or over-use of moisturizers also interfere with natural sebum production and the Calcium ion gradient of the stratum corneum ( The Changes of Epidermal Calcium Gradient and Transitional Cells after Prolonged Occlusion Following Tape Stripping in the Murine Epidermis; https://www.sciencedirect.com/science/article/pii/S0022202X15405603) If calcium is found on the surface of the skin, and sebum plus intercelular lipids (which also eventually make their way to the surface of the skin and mix with sebum and sweat to form the acid mantle) contain cholesterol, wouldn't it be possible then Vitamin D could be synthesised on the skin through irradiation?


texts: What form of reproduction did the first land animals use?

texts:
What form of reproduction did the first animals on land use*? Were they hermaphrodites, or did they have male and female sexes? [Is there a proper term for sexual separation in a species?]

Were any land species believed to have evolved from hermaphrodite ocean species (that crossed to land on roughly the same geological time periods that land creatures first evolved)?

*I know that 'first on land' is a complicated concept itself, since it could mean first creatures be able to survive on land at all, first to freely travel between land and water, or first to only live on land, or anywhere in between.  I assume all three categories were sexual though?


texts: Can roots have cuticle, especially aerial roots?

texts:
In my school biology book, it is written that cuticle covers the epidermal cells in aerial parts of plants and root epidermis doesn't have cuticle. My question is that whether aerial roots, in plants like kalanchoe, also not have cuticle?

Do all kinds of roots not have cuticle?


texts: Do Red blood cells(mammals) really have no organelles?

texts: I have read that mammal mature Red blood cells lack most organelles, including mitochondria, golgi apparatus and an ER. ( https://en.wikipedia.org/wiki/Red_blood_cell#Mammalian_erythrocytes ) This makes sense since there purpose is to transport oxygen via hemoglobin, and according to the wiki, they make any energy needed via glycolysis. But are there really no more organelles in a mature red blood cells? A simple google search did not help me.


texts: Is there any documented evidence for suicide among vertebrates other than humans? Lemmings not accepted !


texts: At which step should I apply a detection filter when preprocessing microarray data? (Before/After normalization, batch effects removal)

texts:
What is the best practice when preprocessing microarray data using a detection filter (on scanner p-value)?

Suppose I have a microarray dataset that I have to normalize with Loess and correct with ComBat. When should I apply a detection filter, relative to the other steps in the process?

In my experimental design, I have two pipelines to test:

Normalize per sample between 0 - 1
ComBat
Loess normalization between samples

and

Loess normalization between samples
ComBat

Is there any best practice for the timing of applying a detection filter?


texts: Could someone explain me in detail what is meant by "TF expression LEVEL", what does it represent and how is it measured? This is for example used in figure 3 of this paper: A census of human transcription factors: function, expression and evolution.


texts: Safety of using industrial water for hand washing

texts:
Industrial water taps are present in most biology laboratories I have been too. There are accompanied by a sign stating "do not drink". So obviously it is not a good idea to drink it.

However I could not find any information or reference concerning its safety for body use. The only indication I could find is that eye wash stations are using potable water instead of industrial water, suggesting that industrial water is not suitable for eye contact - at least.

My question: is it safe to use industrial water available in labs for hand washing, multiple times per day over the course of several years?

I am looking for a precise answer about the possible long term harm of industrial water in this context, if possible with references.


texts: I am wondering what are examples of ancestral eudicots which can be purchased from an aquarium store, and or grocery flower store.


texts: Where can I find mutation datasets for cancer?

texts:
My lab has been using TCGA data (somatic mutations and clinical data) to develop panels of genes and of mutations we expect to see in certain cancer populations. We'd like to validate our panels by checking how they hold up against other cancer datasets.

I know that one resource we can use is the International Cancer Genome Consortium but I'm wondering if members of this forum can suggest a few other places we can get both clinical and somatic mutations data for cohorts of cancer patients.


texts:
Lystrosaurus was the largest creature on land in the early Triassic, why did they need burrows? What were they hiding from?

(less seriously, why were they so ugly?)


texts: NaCl role in CTAB - DNA complex in DNA extraction

texts:
I have a question about the role of NaCl in the DNA extraction process. So for NaCl concentrations under 0.5M, CTAB and DNA molecules can create complexes.
In those concentrations, proteins and other hydrocarbons are still soluble in water except the DNA-CTAB complex. If we raise the concentration of NaCl then the complex of CTAB-DNA will be soluble to water too. Correct me if I'm wrong until now.

So I don't understand something. Why do we use NaCl?

Let's assume that we don't add NaCl. Will the CTAB create complex with DNA or not? As I read CTAB creates ionic bonds with DNA (phosphate groups). So in this situation (without NaCl) CTAB must be able to create complex with DNA too.

So why did we use NaCl? Just to keep proteins and other hydrocarbons soluble in the water or there is something else that NaCl helps in this complex creation?


texts: What's the name of this colorful tiny spider?

texts: Found this colorful spider yesterday in my study. Couldn't find exact match over internet. Does anyone know what spider is this? Is it harmful?


texts: What is the name of this green berry tree?

texts:
Location: South India

Month: May

Location: Outside, Metropolitan.

Tree with berry fruits (poisonous or not, I don't know):

Its leaves:


texts: Electrical field stimulation of neurons: what are commonly used stimulation protocols and which are physiological?

texts:
I am doing a labproject with primary mouse nerve cultures (hippocampus and midbrain) and part of the experiments involve performing electrical field stimulation on these neurons.

For now we have decided on three different types of stimulation:

1 Hz for 20 sec (20 action potentials)
50 Hz for 2 sec (100 action potentials)
20 Hz for 2 sec (40 action potentials) which my promoter said was commonly used

I have been looking for (but not finding) other commonly stimulation protocols, especially those with physiological levels.

Are the protocols I have chosen physiological or not (or under- or overstimulation) and why is this so? I assume neuronal subtype also might play a part in this.
Are there other commonly accepted paradigms for electrical field stimulation of neurons?
How can I stimulate my cells within physiological levels?

Any advice, explanation and or further references to find answers to these questions are appreciated!


texts: Why don't our cells merge when their phospholipid membranes touch each other?

texts:
Membranes of our cells consist of lipid bilayer (with some other components mixed in).  Why wouldn't those lipid bilayers glue to each other and make the cells merge? If you suppose that it's due to additional components in the membrane that prevent them from gluing together, consider the case of liposomes, which don't contain additional components, but seemingly don't glue as well.

I'm primarily interested in quantitative physical chemistry aspect of the matter.


texts: best book for a comprehensive introduction to biology for a computer science graduate interested in undertaking research in bioinformatics

texts: I have a postgraduate degree in computer science, and I wish to undertake research in bioinformatics. I had chemistry but no biology in high school. I have read bioinformatics books like "biological sequence analysis" by durbin and "fundamental concepts of bioinformatics" by krane, etc. But I wish to read a comprehensive book on biology (genetics) that will help me undertake research in bioinformatics properly. I have been considering 2 books: "molecular biology of the cell" and "molecular biology of the gene". Are these books comprehensive enough? Please suggest some good books as I have almost no knowledge of biology at highschool or graduate levels.


texts: Book recommendation on selective breeding?

texts:
I am looking for a good book that gives a nice overview of the science and technics of selective breeding. I am particularly interested in the use of population genetics to support decision in this applied field. So do you have any suggestions?

Below are some examples of question that I would hope that book answers.

If the artificial selection is too strong, it is very likely that some beneficial alleles will disappear. How strong do we decide artificial selection to be?
How do we deal with various lifetime?
How do we deal with species that can have only few babies so that we are obliged to limit the strength of selection to keep a stable population size?
How do we make sure to not reduce the immunologic genetic diversity within the population to zero but only to reduce the diversity of genes that influence the trait of interest?
Is it better to wait to be able to measure the quantity of milk in the sisters of a bull in order to infer about the quality of the bull or is it wiser to directly allow the bull to reproduce to speed things up?
How are the estimations of heritability performed?
How do we measure the impact of various environment of the trait of interest?
Which cultural traits should we allow to spread and which should we stop?
How can we use a correlated trait to infer more simply or more rapidly of the amplitude of the trait of interest?
How much outbreeding should we allow?
When is mutation breeding preferable?

and more globally some questions of the kind:

What are the different solution to artificially inseminate?
Can we select on the spermatozoids?
What financial elements should be taken into before creating a breeding plan?
GWA's studies in selective breeding
What is the relative importance of selective breeding and GMO in current economy and in our current ability to improve strains for our purposes?


texts: Meaning of “cognate genes encode the basic biological functions of proteins”

texts:
In the introduction to a review article entitled “Interpreting the protein language using proteomics” the author uses the term ‘cognate genes’ in a manner which I do not understand:

  Whereas cognate genes encode the basic biological functions of
  proteins, the real-time dynamics and regulation of protein structure
  and function are generally carried out by specific post-translational
  modifications (PTMs) of proteins such as phosphorylation,
  glycosylation and acylation.

What does it mean?


texts:
tumour budding, lymphocytic infiltration and resection margins are established factors that influence the outcome of colorectal cancer (1)

In this context what does "tumour budding" mean?

Reference

(1) A. Bolocan, D. Ion, D.N. Ciocan, D.N Paduraru. Chirurgia (2012) 107:555-563. Introduction/0


texts: Hardy weinberg equilibrium and Wright Fisher model

texts: Is the hardy weinberg equilibrium derived by using a model similar to the Wright Fisher model, just without assuming genetic drift and finite pop size? Both seem to use the same assumptions except Wright Fisher takes into account finite pop size and genetic drift. What is the model used to derive Hardy-Weinberg equilibrium called?


texts: Can monoclonal antibodies be used to transport insulin

texts:
Quick question
Monoclonal treatments in cancer require the drug attached to the antibody which then attaches itself to the neoantigen on a cancerous cell, would it be possible to
transport insulin in the same way?


texts: What are all the possible developmental stages an insect can be in?

texts:
I'm making an app which allows the user to report insect observations. Many bugs may exist in different forms throughout their life time. For example, a butterfly will exist as an egg, a catterpillar, a pupa and lastly as a butterfly. A greenshield bug can live as a nymph and then as an adult.
I want to make one list that contains all morphological stages that insects can be in. Then the user can select the appropriate one for the species he or she observed. My question is: What are the names of these stages? Are there any other stages next to the egg stage, caterpillar/larval stage etc?
Thank you


texts: I know frogs still exist but that doesn't mean there wasn't ever a frog population that evolved into toads. Did frogs evolve into toads because their available swamp slowly went away and toads could survive better without water? Did frogs and toads evolve independently from similar selection pressure for shape?


texts: I have heard that a 'vitamin B17' can cure cancer, but that the medical industry never talks about it, since making it legal would cause them loss of billions. But I have never found a reliable report on whether B17 really works or not. There is a question on 'vitamin B17' deficiency as a cause of cancer (see this post), however, not on 'vitamin B17' as a possible medication for cancer. What are the proposed mechanisms? And is there evidence that 'vitamin B17' really works in curing cancer?


texts: Spatial resolutions in optical microscopy

texts:
I have read that different optical imaging techniques such as  such as wide-field microscopy, confocal microscopy or STED microscopy can theoretically achieve a different spatial resolution.

However, I was only able to find information about the STED microscopy's spatial resolution (5.8 nm) on Wikipedia.

Does anybody know of any references or recommended reading (preferably free) where I can learn more about different optical microscopy methods and how the cope with the diffraction limit?


texts: Does the creation of memory involve mRNAs crossing the synaptic gap?

texts:
There is a diagram from a book titled "Teaching with the brain in mind". The diagram shows

The diagram appears to show that the "creation of memory" involves "messages coded by RNA" moving through an axon and being released into the synaptic gap, whereupon they presumably bind to the receptors on the other side of the synapse.

Unfortunately the book does not seem to provide any sources for this and I have not been able to find any sources corroborating this claim. Can anyone provide any references?


texts: What repairs faster when injured: white matter or grey matter?

texts:
This was the exact wording of a test question given by my biology teacher and she said that white matter would repair faster, because there is a myelin sheath to protect the cells.

Do you agree with this answer? Could you give me a more detailed, real life (not school, but real neuroscience, real data) explanation?


texts: Are blood vessels classified as organs? Organs compose of 2 or more tissues and perform a certain function. Blood vessels have 3 different tissues and perform a function (transport blood), yet I do not see them being identified as an organ. Why is this? Are they organs? Or do they hold their own classification?


texts: Help with understanding XKCD's “How Vaccine Failure due to Viral Vector Immunity Works” Why is this response a failure exactly?

texts:
Full disclosure; no biology since 9th grade, so please go easy on me!
XKCD's 2406 shows a literal wooden Trojan Horse outside a castle, but instead of bringing it inside the castle walls, the soldiers recognize the shape as horse-like:

Look! It's a statue of that horrible animal that trampled Steve!

and the soldiers decide to destroy and dispose of it rather than to let it in.
The title of this XKCD is

Viral Vector Immunity

with the subtitle

How Vaccine Failure Due to Viral Vector Immunity Works

Wikipedia's Viral_vector; Vaccines explains the basic idea, which is (I think) that the viral vector's genome is modified so that it includes a new protein on its surface that serves as an antigen, and the host builds and learns an immune response to this antigen that will then immunize the host against an infection by another organism that also presents this antigen.
Question: The XKCD shows recognition and an analogy of an immune response, so why does the subtitle call this a "Vaccine Failure"?

XKCD image License


texts: The truth behind human urine and marking territory?

texts:
So some years ago, I remember watching a survival show in which the host said that human males produce a type of chemical in the urine that animals such as wolves can acknowledge as a territory marker. The host also said that women do not produce it, and therefore cannot mark territory in the same way men can.

Would this be accurate? Would the results of this change at all if the individual was a fully transitioned transgender person?


texts: What are the limitations to current nucleotide sequencing technologies?

texts:
Using the Illumina platform, it is cheap and (relatively) easy to sequence huge amounts of DNA or RNA. There are various other platforms out there (Roche/454, SOLiD, PacBio, Ion Torrent) each with their own distinct advantages, but Illumina seems to be pretty popular for many applications, despite its limitations.

Ideally, we would like a sequencing technology that produces long, error-free reads with high throughput. However, at this point it seems we have to make a choice: throughput or length (and quality). PacBio seems promising, but the last I heard they have still been unable to deliver on their claims.

What are the molecular and biochemical limitations to our current sequencing technologies? Why don't we already have long, error-free reads with high throughput?


texts: Molecularly, why can you straighten or perm hair?

texts:
I'm aware that hair can be curly because of the disulfide bond interactions in between cysteine amino acids in alpha-keratin filaments. However, I'm curious as to the biochemistry involved in straightening hair with a straightening iron, as well as with "perming" hair.

What happens at the molecular level? I suspect that a straightening iron simply disrupts the present disulfide bonds, but I'm only speculating.


texts: condensed protocol for sequencing a portion of human DNA from buccal sample

texts: Anyone have a short & sweet protocol for PCR amplifying a region of human DNA (chromosomal or mt, I don't care) extracted from a buccal sample: including validated primer sequences and preferred method of DNA isolation from a buccal swab. I'm looking for a new exercise to run in my classroom. We would be able to follow the amplification up with Sanger sequencing, done in-house.


texts: What is a good book to start with if I'm interested in Gene clustering analysis?

texts:
As a beginner, I would like to learn more about gene clustering analysis, namely discovering groups of correlated genes potentially coregulated or associated to some conditions or finding patterns in gene expression data, identification of coexpressed genes from microarray data.
I was looking up for some books, but all of them are a little too much biology-heavy for me, given the fact that I have a Computer Science background. I would like to dive into algorithms such as hierarchical clustering, k-means algorithm, pattern-based clustering and other methods, so a book addressing these would be of real help.
If you have any suggestions, I would be grateful.


texts: What is the ratio of breathing rate to heart rate?

texts:
Breathing rate and heart rate are directly connected. This is because the heart is connected to the lungs via the pulmonary artery.

I first thought that breathing rate would be half of the heart rate since half of the heart cycle occurs in the lungs.

But I know that is not true with a normal 12 BPM(breaths per minute) breathing rate.

So what is the ratio of breathing rate to heart rate?


texts:
Considering the kegg page, this page contains the description of the gene Edwardsiella tarda EIB202: ETAE_0074 . Now this gene has a name given in the page as : wabG.
Now considering another gene 1 and gene 2 , what is the name of these genes? How to I find the name of these gene and from which website?


texts: The wikipedia article on the dopamine transporter gives examples of some drugs whose effects are mediated by the inhibition of the dopamine transporter, such as cocaine and amphetamines.  Are there any drugs or substances whose mechanism of action involves increasing the activity of the dopamine transporter, i.e., a "DAT releaser?"


texts:
I've been thinking about this for a while and I can't figure out how a memory can be stored in the brain.

I understand that important memories are favourably retained, such as a near death experience, the birth of your child or your wedding day. But I cannot comprehend how this can be stored biologically in the brain.


texts:
Im doing different analysis of the human chromosomes and diffent loci, however when using different databases, the heterochromatin structures are not part of the human genomes. I know that heterochromatin is a more dense structure within the DNA and stained differently and are not part of the different reference genomes.

However all the information regarding the human chromosome sizes, I can find all includes the heterochromatin regions.

So i would like to know, is there anywhere i can find the length of the human chromosomes without the heterochromatin structures?

Thanks for your time and help.


texts: Can any species be bred selectively/engineered to become as diverse looking as dogs?

texts:
I've done some research and it appears that dogs are the most diverse looking single species of mammals. The questions that interest me is - are dogs special in respect to genes/gene activation mechanisms related to appearance? Or does this dramatic difference in appearance have something to do with dog anatomy and how they give birth?

If dogs are not special, this makes me interested if other species of mammals can also be bred selectively (or genetically engineered) to produce such dramatic variation?


texts: What is the scientific name of this evergreen plant?

texts: This plant is found in India. It is an evergreen plant. Would love to know the scientific name.


texts: Why doesn't the soil get depleted after repeated clearing of vegetation?

texts:
In my neighborhood, there is a hillside owned and maintained by the local municipality.  The hillside is generally overgrown with vegetation.  Work crews clear out the vegetation multiple times throughout the spring and summer, yet it always grows back quickly.

The workers don't leave the cuttings there.  They haul them away.  So that means the soil of the hillside is losing nutrients.  Yet why does the vegetation always grow back?

Hypotheses:

It all looks like weeds to me, but maybe there is a natural cycle of crop rotation going on that I can't appreciate.  I.e., in year 1 it was all Type A weeds, then in year 2 it was all Type B weeds, then in year 3 it was all Type C weeds, and then in year 4 it was back to Type A weeds again.
Maybe some other natural process is bringing nutrients back to the soil of the hillside.  Bird droppings?  Earthworms?  Insects?  Underground fungus and bacterial colonies?  Small mammal feces?  (I don't think rain runoff is bringing many nutrients because there is nothing but a highway above the hillside.)
Maybe the hillside is getting depleted and will eventually become barren, it just takes a while.  I guess you have to keep clearing, year after year, until it gets down to the very last and most hardy of the weeds before it becomes truly barren and lifeless.


texts: Can the "Cas9"(involved on the Crispr-cas9 mechanism) be considered as a restriction enzyme?

texts:
I have many questions about the Cas9 enzyme. When the Cas9-guideRNA (crRNA and transcrRNA) complex is attached to the DNA sequence, what is the type of bond that cuts the Cas9? Does the Cas9 degrade all the sequence of DNA complementary to the guide RNA?

If the question before is "Not", then how is the sequence that is going to be cut on the DNA complementary to the guide DNA, determined? What type of enzyme the Cas9 is?


texts: If we introduce any disease or deadly effect to a large group of living things, will such a group be able to develop a resistance?

texts:
Like for instance, introducing cancer or radiation,
to a large group of insects/animals that can reproduce very quickly,
would it result in the surviving population of these living things to be more resistant to whatever adverse condition that was subjected upon it?


texts: Analysis of post transplantation lineage tags

texts:
I'm having some trouble understanding some bits of a study, mostly about the Sleeping Beauty system and TARIS model, from this paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4408613/

I understand the concept, but not how it works technically. Can anyone explain it for me?


texts: Confusion regarding niches in evolution theory

texts:
This is the definition of a niche from Crash Course:

  An area of the environment that requires a special set of skills or traits to extract food and reproduce.

Obviously, this version of the definition has been dummed so that it appeals to mass audiences, but after some research, I believe that the general concept remains the same.

Here is what I've learnt about species living in a niche:

The more the competition, the slower the evolutionary process.
Lack of competition provides an ideal environment rapid evolution.

But these points seem non-intuitive to me, because:

Why would a increased competition slow down the evolutionary process? Shouldn't it speed it up, as different species will try to evolve the fastest in order to beat adversaries?
Why does a lack of competition promote rapid evolution? Won't it slow down the evolution, as there is no reason to evolve?

I know that there is a logical reasoning behind this, and I would very much like to understand it.

My source is Crash Course, specifically this  video. I've found it to be extremely reliable over the past, and highly doubt that they are supplying incorrect information. If anything, it is probably my inability to understand the concept.


texts: Is it necessary to calculate lane normalisation factor when doing western blot data analysis?

texts:
I have recently done my first western blot and I am doing data analysis to quantify my blot. I have labelled my membrane against inactive GSK3 and active GSK3 which are phosphoproteins so I am using total GSK3 as an internal loading control. I have read some guides and handbooks  about western blot data analysis and I have seen that some of them calculate a lane normalisation factor to account for variations in signal intensities of the loading control. For all loading control bands in each lane, they divide by the loading control band with highest intensity to get the lane normalisation factor. Then for each band of the target protein of interest they divide by the lane normalisation factor to get the normalised intensity.
I was wondering in general with western blots is it good practice to calculate the lane normalisation factor when doing the data analysis? Any insights are appreciated.


texts: Reliable recipe to make DIY yeast slants

texts:
Does anyone have any good ideas on a reliable way to activate basic grocery store yeast?
I realize this is a total beginner's question.  I've built a small yeast ranch at home with my kid, and we're trying to learn how to innoculate agar'd petri dishes with home grown samples we're trying to make from basic grocery store yeast.  Eventually, want to do more advanced experiments, but for now...we're just looking for some growth.
So far, our best attempts at using grocery store yeast packets have yielded no results (i.e. no visible growth).  My best attempts to find a good recipe have lead nowhere.  I see lots of good advice on how to follow sterile procedure on making agar'd dishes and how to innoculate from an existing slant; but we thought it'd be easy to just start with grocery store yeast instead of buying a slant.
FYI -- there's obviously some kind of growth happening on the petri dishes.  When we break from sterile procedure and invite contamination; then it's clear something (not yeast) is happily growing on the plates.
My mistakes that could've lead to zero growth on the petri dishes include:
(A) Perhaps adding the dehydrated yeast to water that's way too hot?
(B) Perhaps I did not add enough wort or sugar for the yeast to feed on?
(C) Maybe i should've let the dissolved yeast ferment for a while before innoculation?
Would very much appreciate any help from someone more experienced on this.
best wishes...


texts: How much variation in mutation rate in there in the human genome?

texts:
In humans, the average mutation rate is estimated to be around $2.5 \cdot 10^{-8}$ (Nachman and Crowell, 2000). Of course this mutation varies from sequence to sequence.

Can you please give some ideas of how much variation in mutation rate there is in the human genome?

There are many ways to express such variation. One could give the lowest and highest mutation rate or shows a mutation rate map over either the whole genome or a randomly chosen sequence.


texts: If some humans inherited 3% of Neanderthal DNA, why are we 99.9% same genome?

texts:
Many sources say that humans are 99.5 to 99.9 percent the same.

Also some sources state that some humans have 3.4% Neanderthal DNA and some don't share those genes.

Why is that?


texts: So I know that it’s not from tears or sweat because they are composed of mainly water and sodium, it’s not from going poo or pee as poo and pee are made of the parts of food that supply your body with no nutrients and your body also doesn’t “burn body fat” because there is a theory that no matter is ever destroyed so it’s none of those but another thing is it’s not your hair, ear wax, finger nails or anything of that sort because people can lose over 17 pounds in 3 months but you can’t build up that amount of hair , ear wax or whatever else in three months so how does body fat leave your body


texts: So I was cleaning out my car and found a McDonalds French fry. as I don't eat anything in my car I know exactly who and when this fry is a result of. The when is + 10 months old and it could pass off as one just prepared. How could this be?


texts:
We know that during the crossing over of meiosis II, some portions of the paternal chromosome recombine with the maternal chromosome along the  chiasmata. And the number of chiasmata varies.
My question is this: If the crossing over is responsible for genetic variation, then does the number of chiasmata increase in the same chromosome in the same species for the sake of the species' survival? And if so, what factors contribute towards increasing that number?


texts:
Can anyone identify this organism please? Often I see it inside my home on the walls moving very slowly.
please click for a better-quality image

some more info:

Geographical location: India (north part)
Image taken recently (March 2018)
Size of organism: about 1 cm in size.