Submitted by Which-Community-5851 t3_11njmq7 in askscience
Tropenpinguin t1_jbqmuh9 wrote
Reply to comment by xilog in Why are Y chromosomes shorter than the X chromosome? by Which-Community-5851
SRY is like a conductor. It triggers the multiple genes to express testes or suppress ovaries. But those genes also trigger and suppress other genes. And while SRY is the trigger in some mammals, it's not necessary to kick start sex determination.
For example the platypus has five pairs of sex chromosomes. Females are XXXXXXXXXX and males are XXXXXYYYYY. Despite that many Y, on none of them SRY is found. One of those other interacting genes triggers sex determination. What's even more interesting those various involved genes can be found in similar combination throughout all vertebrae, but the trigger differs.
So while SRY is the trigger in some, it's not the only one.
xilog t1_jbqqfgg wrote
TIL! Thanks :)
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