Because of defects, the standard definition is, and needs to be asserted as, Y presence is male, Y absence is female. Y presence is determined solely by the sperm and is regulated by the presence or absence of the SRY gene.
Klinefelter syndrome is XXY males, 1 in 2,500 males diagnosed, possibly 4 times as frequent undiagnosed. There are several other defects. 99.9% is perhaps a fair order of magnitude.
Because of defects, the standard definition is, and needs to be asserted as, Y presence is male, Y absence is female. Y presence is determined solely by the sperm and is regulated by the presence or absence of the SRY gene.
Klinefelter syndrome is XXY males, 1 in 2,500 males diagnosed, possibly 4 times as frequent undiagnosed. There are several other defects. 99.9% is perhaps a fair order of magnitude.