Discussion about the role of 'epistasis' is complicated because the term has different meanings in biochemistry/molecular biology and in population genetics. Biochemical epistasis occurs when two genes have products that interact in a single pathway. Population-genetic epistasis occurs when two loci are polymorphic and there is a statistical interaction between alleles at the two loci in their effects on fitness. One can have one sort of epistasis without the other, and it is not always clear which definition people are using.

That clears up a confusion that I've had for a long time. I was trying to make sense of two different definitions as if they were one.

then i need to be a better communicator! i thought i'd addressed this issue implicitly in several posts....

The key point that I missed (it may well have been in your posts!) is that the two definitions are totally independent of one another.

well, statistical epistasis is often a subset of biochemical epistasis. that is, a single pathway may be modulated by two loci (biochemical epistasis), and the nature of that modulation is contingent upon the alleles at the loci in question (statistical epistasis).

well, statistical epistasis is often a subset of biochemical epistasis.

That could be why I was confused, because it's not necessarily so.

question 5 popped out at me. Very cool. someone needs to do that with south american monkeys. and with us.

questions 1 and 4...too too true

question 8, I could've sworn they've done before. some kind of mammal embryo where maternal gene expression and paternal gene expression (for some gene) in the brain were concentrated in completely different areas.

I know I saw a pretty picture involving something like that.

I've read that children look more like their fathers, and begin to resemble their mothers more as they age. Supposedly this is an evolutionary adaption so that fathers can be sure that they children are really theirs, and will be more willing to devote resources to them. Would this be an example of genomic imprinting in humans? Obviously for the child to look more like the father, the genes for the father's appearance would have to be distinguished from the genes for the mother's appearance.



10) If you could change one thing about your educational path, would that be?

I would have learnt more linear algebra as an undergraduate.


Is there anyone who does graduate school in science and engineering who doesn't share this regret?

lol, I was about to say I did take it in undergrad but haven't used it yet in grad school or research. then i realized i was lying through my teeth.

I've read that children look more like their fathers, and begin to resemble their mothers more as they age. Supposedly this is an evolutionary adaption so that fathers can be sure that they children are really theirs, and will be more willing to devote resources to them.

this wouldn't be an asset in the case of a situation where the attributed father isn't the father :)

I think this is what he was thinking of:

Whom Are Newborn Babies Said to Resemble? (PDF)

"Said to" is the key phrase; they don't appear to really look more like fathers. (PDF)

This paper ties it together. It's in everybody's best interest that the baby doesn't resemble anybody more closely (as it doesn't), and in everybody's best interest to convince the father it's his (as they do), and in the fathers best interest to believe them.

Here is a basic discussion of genetic imprinting from Haig.

Razib says:


7) In a follow up in regards to accumulation of deleterious alleles, in The Cooperative Gene Mark Ridley suggests that spontaneous abortions are purging the genetic load from our population. If survivability and reproductive value of individuals who carry a high load of deleterious alleles in elevated in our modern population, that seems to imply to me that spontaneous abortions would be elevated as well, perhaps serving as a check on the accumulation of load. Is this possible?


Hmmm, if an individual could have some self knowledge of a high load of deleterious alleles, it migh be in their interests to take risks with sexual partners. Females might be able to take more risks than males ...

To elaborate on my comments, I would imagine that males with a high deleterious allele load would tend to remove their gene combinations from the gene poole, while females would tend to perpetuate them ... such females might be better served by having female offspring as well.

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