Sex is set, or “determined,” when an X chromosome from an egg finds itself in a nucleus with an X or a Y from a sperm. XX=female: XY=male.
For six weeks, the embryo unfurls two sets of “indifferent” gonads, with two sets of plumbing. At week 6, a gene on the Y called SRY, for “sex determining region of the Y,” turns on and the fledgling female parts shrivel away. Without SRY, and under guidance of other genes, the male structures vanish instead. So anatomically we all start out with a bit of both.
Mess with the genes and chromosomes behind our sexuality, and mismatches arise. A mutation in a gene called Wnt4, for example, disables the switch to femaleness, and an XX embryo drowns in testosterone. Vagina, cervix, and uterus never develop.
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Most fascinating is 5-alpha reductase deficiency, in which life begins as a girl, based on appearance…At puberty, the adrenal glands release testosterone…and then the voice deepens, facial hair grows, and instead of developing breasts and menstruating, the clitoris swells into a penis and sperm are produced.
Related on the SLP
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A genomewide SNP screen, or even genome sequencing, might one day identify a genetic “signature” for individuals more likely to identify as transgender. Should we even go there? I don’t think so. What good could it do? People who identify as transgender already know it – it’s certain others who have a problem with it.
The GLP aggregated and excerpted this blog/article to reflect the diversity of news, opinion, and analysis. Read full, original post: Is Transgender Identity Inherited?
