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View Full Version : Are Y-DNA SNPs more a function of age (continuous cell division) or generations?



newm1988
08-25-2019, 04:32 PM
I'm guessing this question has been asked before but I haven't found a thread for the answer.

Are Y-DNA (or for that matter autosomal or mtDNA) SNPs and STRs just a product of ordinary cell replacement and division or is there something about the last stage of spermatogenesis (or oogenesis for women) or fertilization that tends to cause mutations to occur at a markedly higher rate at that stage?

Consider the following hypothetical over a 2000 year period:

Line 1 is made up of men who have children when they are exactly 20 years old, so 100 generations over 2000 years.
Line 2 is made up of men who have children when they are exactly 40 years old, so 50 generations over 2000 years.

Would we expect the rate of Y-DNA SNPs or STRs to be significantly different on average between the descendants of these two lines? If so, by how much and what would cause the difference?

For that matter, if somehow a man could live a relatively healthy life to be 1000 years old, and you tested the man at age 20 and age 1000, would you expect to see a difference in SNPs or STRs between the two tests?

MacUalraig
08-25-2019, 05:31 PM
There are far more cell divisions in gametogensis in men than in women and for men the number rises with age unlike with women. Jobling and Tyler-Smith cite as an example that an octogenarian male's sperm has had 40x as many cell divisions as a 15 year old. So yes old men have undergone more chances of both SNP and STR changes.

see Human Evolutionary Genetics 2nd ed Jobling and Tyler-Smith.

JonikW
08-26-2019, 05:35 PM
There are far more cell divisions in gametogensis in men than in women and for men the number rises with age unlike with women. Jobling and Tyler-Smith cite as an example that an octogenarian male's sperm has had 40x as many cell divisions as a 15 year old. So yes old men have undergone more chances of both SNP and STR changes.

see Human Evolutionary Genetics 2nd ed Jobling and Tyler-Smith.

Thanks. There could be implications for Y match dating based on the long-standing social status of each of the families involved and even their countries of origin (given that the poorer people are, the less likely they've generally been to procreate when older and survive to an advanced age). I wonder if anyone's ever looked at possible trends regarding the number of unnamed variants to common ancestors for people who are Y matches but from markedly different economic groups.