Dictionary of Human Evolution and Biology

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Sex-determining Region Of The Y Chromosome

Among the very few genes which have been mapped specifically to the Y chromosome. SRY is a testis-determining transcription factor located on the pseudoautosomal region. The SRY gene product occurs in male gonadal tissue at the time of sex determination; in humans this is about the sixth week of development. SRY binds to DNA, distorting its shape, and alters gene expression at the binding site. It is suspected that this starts a cascade of activity in genes located on the autosomes; these are then expressed either differently (or only) in males than in females. All Theria (marsupials and placental mammals) have the SRY gene. When transferred into normal XX female mouse genomes by means of the new genetic technology (creating transgenic species), SRY DNA fragments induce testis differentiation in those females. Aka TDF, or testis-differentiating factor.

See ambiguous genitalia, pseudohermaphroditism, XX male, and XY female.

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