5 replies to this topic

[brokenportal]

Why doesnt sperm DNA misreplication seem to happen as fast as the rest of the cells in a persons body?

I would think that if generations of people kept having kids at the age of 30 that the sperm cells would have x amount of misreplicated codons in the second generation, x+y misreplicated in the third, x+y+z after the fourth and so on until the DNA is completely ablated.

Why do our body cells do that but sex cells dont?

[John Schloendorn]

As your subtitle suggests, one important aspect is certainly selection:
- Natural selection: Individuals with deleterious mutations are often selected against before they reproduce.
- Mate selection: Those with less severe, but instinctively detectable mutations may not get the chance to reproduce, by not being picked, being victim of adultery, ect.
- Cell selection: With sperm the race mechanism makes sure only fully functional cells can fertilize. I believe, with eggs the mechanisms are less clear.

[brokenportal]

Yes, but sex cell degredation from generation to generation should still appear in everybody right? So I would think that even the strongest healthiest people would go exponentially down hill with each new generation and that the strongest and healthiest sperm would do the same.

I know we select the healthiest, and the healthiest get to the egg first, but why arent succeeding generations coming up with a line of healthiest people who are succeedingly less and less healthy than the last generations line up of the healthiest people?

[John Schloendorn]

I guess that's why we have sex. Whenever one individual has a DNA error, the offspring can get fixed by recombination from the other parent who doesn't. Add to this the high intrinsic DNA repair activity in the germ line and we may be getting there.
I'm not saying I explained the problem away. Many details of this are to be worked out. But I guess this is the direction the explanation will take.

[brokenportal]

So there is a lot of DNA repair activity in germ cells? Im going to have to read about this. That was exactly the kind of lead I was hoping to find by asking the question, thanks. Then the combination with the other parent.... Now that I think about it, Im going to have to reexamine the process of germ cell division and everything under this light. Ill have more questions for you and everybody once I look it up.

Can you give any details about the nature of intrinsic DNA repair in the germ line?

[John Schloendorn]

Hmm some repair enzyme activities are sort of higher, but not as high as one might expect... Sorry I don't know much detail.