This is quite amazing and could prove to be a significant finding for the field of developmental biology, and it might not have been discovered if it weren't for prenatal genetic screens. Check it out (from NewScientist):
A seven-year-old girl with a Y chromosome is providing new clues about a possible "master switch" of maleness.
The girl has the normal chromosome count – 46 – and should be male. Other children who have the male sex chromosome but do not appear to be boys have been found to have gene mutations that temper the Y chromosome's effects. However this child doesn't have ambiguous gonads, shrivelled testes or other developmental defects. She instead has a normal vagina, cervix and set of ovaries.
A team led by Anna Biason-Lauber, of University Children's Hospital in Zurich, Switzerland, thinks the patient's normalcy is due to mutations in a poorly understood gene on chromosome 17 called CBX2.
The child's unique condition might not have been discovered were it not for tests performed before birth to check for major genetic defects, such as an extra copy of chromosome 21 that causes Down's syndrome. Those tests came up negative and indicated the child would be a boy.
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