Scientists from the University of Michigan have discovered why some couples have only boys, while others only have girls. It turned out that genetic variants of RLF and KIF20B influence the sex ratio. The study results were published in the journal Proceedings of the Royal Society B: Biological Sciences.
According to scientists, approximately the same number of boys and girls are born around the world every year, but in some families, some couples have all children girls, while others have boys. This phenomenon attracted the attention of researchers to the possible role of parental genes in this process.
To study the potential genetic factors behind same-sex births, scientists analyzed data from the British Biobank, which contains information on 500,000 Britons. The study identified a single nucleotide change rs144724107, which increases the likelihood of having a girl by 10%. However, this change occurs in only 0.5% of participants. It is located next to the ADAMTS14 gene, which is involved in the processes of spermatogenesis and fertilization.
In addition, the researchers found two other genes, RLF and KIF20B, that may also influence sex ratio. However, according to scientists, the properties of these genes require additional testing in other samples.
The findings are consistent with Fisher's principle, a theory in evolutionary biology that explains why populations maintain equal sex ratios. If more individuals of the same sex begin to be born in a population, natural selection promotes an increase in the birth rate of the “rare” sex, which leads to the restoration of equilibrium.
