Sex Determining Region Y

Sex Determining Region Y

In mammals, the X and Y-chromosomes determine the sex of an organism. If a mammal is homologous XX than that mammal will be female and if the mammal is heterozygous XY that individual will be male, assuming no mutations. What is it about the Y chromosome that dictates the male sex? On the short arm of the Y-chromosome is a region called the sex-determining region Y or SRY that codes for transcription factor “sex-determining Y” protein in mammals. In 1991, the function of SRY was revealed to be the sex-determining gene in mice that was responsible for testes formation. This was determined in a study where homologous XX mice (female) had been introduced to SRY and subsequently became male (Koopman et al. 1991).

SRY is part of the SOX transcription factor family. Like others in its family, SRY has a high mobility group or HMG DNA-binding domain which is about eighty amino acids long that is structurally related to other domains in the SOX family. The domain has a specific binding sequence, AACAAAG or AACAAT, that is binds to and a particular angle it bends at when it binds to the specific sequence, where both the sequence and the bending angle are crucial for function (Harley and Goodfellow 1994). In human females that are XY, many have mutations in the HMG domain, again supporting the importance of the domain sequence for function and when SRY is not expressed, genes express female-specific traits and induce ovarian development. (Harley and Goodfellow 1994).

Among animal species SRY, besides the HMG domain is not highly conserved and varies between species. Many studies involving SRY have used the mouse as a model. In an XY mouse embryo at 10 days post coitum or dpc, gonads arise from the genital ri...

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