The above figure is from Common variants spanning PLK4 are associated with mitotic-origin aneuploidy in human embryos. The author has presented this work at meetings, so I knew it was pending. One of major angles here is that you now have an actionable genotype whereby one can make calculations of likelihood of aneuploidy.. If you are female, and have a 23andMe account, just click here. In accord with the results above the risk for aneuploidy is as follows AA > AG > GG. If you don’t have access, the supplements have a lot of interesting stuff. There you can see that there’s no discernible geographical distribution of the minor allele, which is present in ranges from 20 to 40 percent (here it is at the 1000 Genomes Browser).
From an evolutionary perspective the strange thing is that the derived allele seems to reduce reproductive potential. Neandertals don’t carry the derived variant. But the presence of this derived allele isn’t a coincidence, the authors detect an ancient selection event around this region. So either the variant is beneficial in some way, or, aneuploidy as a trait has hitchhiked. I’ll post the explanation in the paper here, because I honestly don’t even know what to say:
The fact that the haplotype bearing the derived allele did not sweep to fixation and is present at similar frequencies across human populations is consistent with the action of long-term balancing selection. We speculate that the mitotic-error phenotype may be maintained by conferring both a deleterious effect on maternal fecundity and a possible beneficial effect of obscured paternity via a reduction in the probability of successful pregnancy per intercourse. This hypothesis is based on the fact that humans possess a suite of traits (such as concealed ovulation and constant receptivity) that obscure paternity and may have evolved to increase paternal investment in offspring (24). Such a scenario could result in balancing selection by rewarding evolutionary “free riders” who do not possess the risk allele—and thus do not suffer fecundity costs—but benefit from paternity confusion in the population as a whole
Whatever is happening is very strange. The authors make the case that there ascertainment bias is such that they’re underestimating effect of the derived variant. All things equal the selection coefficient should be strongly negative.
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