Evolution of the testis-determining gene--the rise and fall of SRY.
The mammalian Y chromosome has been known for a long time to harbour a gene that triggers testis determination, and this testis-determining factor was identified as SRY in 1990. It has been supposed that SRY was the original mammalian sex-determining gene that initiated the differentiation of the Y from the X early in mammalian evolution, and this belief has been reinforced by an analysis of divergence times. However, I will argue here that SRY evolved quite recently in therian mammals and was not the original mammalian sex-determining gene that defined the X and Y. It arose as a degraded version of the X-borne SOX gene that is better qualified to be a brain-determining gene. It has no central role in sex determination, and can be replaced as a trigger and lost, as have many other Y-borne genes in recent evolutionary history. The mole vole has evidently accomplished this.
Graves
Jennifer A Marshall
JA
Research School of Biological Sciences, The Australian National University, Canberra, ACT.
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D019143:Evolution, Molecular; D006609:High Mobility Group Proteins / Q000502:physiology; D006801:Humans; D008297:Male; D008322:Mammals; D009687:Nuclear Proteins; D055748:SOXB1 Transcription Factors; D019849:Sex Determination Processes; D051876:Sex-Determining Region Y Protein; D013737:Testis / Q000502:physiology*; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D009687:Nuclear Proteins; C527785:SOX3 protein, human; D055748:SOXB1 Transcription Factors; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors