When we talk about sex and human development, certain chromosomes tend to come up in the discussion: specifically, XX or XY. It’s worth stating from the outset that this is not true for everyone; some people are born intersex, while others have a set of chromosomes that can result in Klinefelter Syndrome. But for most people, chromosomes determine sex — at least, that’s the accepted science. But what are the odds of a child being one sex or the other? You’d think it’s approximately 50/50 — but what if it wasn’t?
Now, a group of researchers has probed that question with the release of a paper that explores the influence of other genes on a person’s sex. It’s worth stating up-front that the paper, published at bioRxiv, has not been peer reviewed. Still, the assertions made within it have led to some scientific debate over the conclusions contained within.
The authors begin by bringing up “[s]egregation distortion,” described here as “the disproportionate inheritance of selfish genetic elements.” Drawing on records from the Utah Population Database, they discovered evidence of “a family that preferentially produced male offspring at a 2:1 ratio.” They note that in the first generation of the family, one father had six children, five of which were sons; in the second generation, one father had 11 children, eight of whom were sons. Overall, the scientists recorded 89 children in the family; 60 of them were male.
In their paper, these scientists point to the existence of “Y-chromosome distortions” that can lead to a larger percentage of male children in families than the expected 50/50 split. Not all experts on the subject are on board with this line of reasoning, as Nature‘s Ewen Callaway reports. One scientist in particular, the University of Michigan’s Jianzhi Zhang, cited a few reasons for skepticism.
Y Chromosome Loss May Impact Men More Than Previously Thought
Scientists have long known about the age-related chromosomal loss, but it is now being associated with serious diseasesZhang told Callaway that it was possible that some female births in the family were not recorded in the state database. He also questioned whether the Y chromosome was a likely location for such an impactful genetic factor. “In the future, it would be very interesting to identify the molecular nature of the distorter and the distortion mechanism involved,” he told Nature.
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