system
Given the following post, respond as if you're commenting on Reddit:
human
are two puppies who are litter-mates more related to each other than to a puppy born in another litter, but to the same parents?

Does sharing a placental environment affect the relatedness of the puppies?
gpt
The puppies will have exactly the same genetic relatedness, but there is a chance they end up sightly more similar to one another than to a different litter based on the effects of non-genetic influences. For example, the environment and experiences they all share after birth during the critical socialization period, which might be different for each litter, and which can be profound in their effect on behavior in dogs. (One reason why cloning will never actually get your beloved pet back- you simply cannot duplicate all the variables even if the genes are identical.) Or before they’re born, the mother may experience some level of stress or illness that may prime the puppies to respond to stress slightly differently. Also, there’s a prevailing theory that mild illness in the pregnant mother dog, or unusually cold temperatures, can both contribute to slow melanocyte migration in the fetuses which is why some “solid colored” dogs are born with incidental tiny white snips on their toes, chins, tail tips, or the center of their chest or belly, as these are the last places those cells migrate during development, and this doesn’t seem to be heritable (though the tendency to be susceptible to this effect might be heritable, that doesn’t seem to be cleared up yet, and most heritable genes for white also follow a similar pattern of slowing melanocyte migration even in ideal conditions, which is why if a dog is going to have white it’s most likely going to be socks/ruff/blaze etc). In that case one litter of a certain purebred might have tiny show faults if the mom was going through it during her pregnancy, and another might not. But the actual genetic relationship between all the puppies would still be full brother and sister.