Skip to main content
Sign In

Welcome to the University of Colorado School of Medicine.

University of Colorado School of Medicine

Cell Biology

I've studied meiosis so I have an idea of how that process renews DNA in offspring. What I don't understand is how the DNA in the mitochondria is renewed. It seems that there must be a process or the mitochondrial DNA would degrade and become susceptible to damage within a couple of generations. What's the story here?

Each mitochondrion contains about 2-10 copies of the mitochondrial DNA (mtDNA), which unlike the nuclear DNA, is circular like the DNA molecules of bacteria. mtDNA codes for 13 proteins involved in energy production, plus specific proteins involved in its own replication, including polymerases. The nucleus supplies many other proteins for mitochondrial function. When a cell is ready to divide it replicates its mitochondria. The DNA is duplicated in much the way that it is in bacteria, using what is called a D-loop mechanism: one strand replicates until it reaches the origin of replication of the other strand, and then the process continues in the opposite direction.

Please explain/describe MGUS, multiclonal gammopathy of undetermined significance.


Is SNP measureable? If so, how?

Single nucleotide polymorphisms can easily be measured on “gene chips” some of which can compare 5 million or more SNPs between different people’s genomes.

From Bob-Does cell mutation increase the chance of cancerous or "misbehaving” cells?

Yes, there are many mutations that take place between the initiation and final development of cancer.

Is it possible to change the DNA of an embryo, and can you duplicate DNA by human manipulation? From Jessica

Yes, we can repair genes in mouse embryos, and can add new ones, for example, normal or mutated human genes to see the effects on mouse development and learn what they might be doing in humans. We have not yet tried adding or changing human embryonic genes.

Does the term "well differentiated" in cancer terminology refer to cells? If so, what does it mean? The diagnosis was a "well differentiated adenocarcinoma."

Well-differentiated refers to the overall look of the tissue; does it look like a normal tissue, or very abnormal? So a well-differentiated adenocarcinoma looks a lot like normal glandular tissue. It is usually a good prognostic sign.

Can genetic information be done to detect future illness and be treated early?

Absolutely, we already do this, for example by screening all newborns for phenylketonuria (PKU) which is devastating, unless it is diagnosed early and the patient put on a phenylalanine-free diet; then they can be perfectly normal.

When do doctors do the genetic testing for diagnosis? Does the fact that DNA is wrapped &/or coiled so tightly help to protect the bond from free radicals? Therefore, is DNA more vulnerable when it is unzipping?

There are routine screens of newborns, when identification can lead to prevention. And there are adult human genetics labs that can screen for genetic variants that can be significant, for example certain variants of the BRCA gene with high association to breast cancer. The uncoiling is brief and not in itself associated with increased mutation; but only when DNA replicates do mutations become “locked in."