A SEVEN-year-old girl with a Y chromosome is providing new clues about a possible 鈥渕aster switch鈥� of maleness.
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鈥檚 effects. They generally have indeterminate gender characteristics such as ambiguous gonads, shrivelled testes or other developmental abnormalities.
This child has the physical attributes of a girl, however, with a normal vagina, cervix and ovaries, according to a team led by Anna Biason-Lauber of , Switzerland (The American Journal of Human Genetics, ).
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She lacks the gene mutations present in the other children but has mutations in a gene on chromosome 17 called CBX2.
CBX2 has aroused interest as a possible master switch for maleness because tests in human cells suggest that mutations in it can shut off a gene on the Y chromosome critical for male sexual development.
If so, it would explain this girl鈥檚 lack of male physical characteristics despite her having a Y chromosome.