Sex-Determining Function of Gene Backed by Studies

Scientists say they have new evidence that a recently discovered gene plays an important part in determining an unborn baby’s sex.

The idea is that a fetus who inherits the gene will be male and one without it will develop into a female.

The scientists studied rare females who had inherited the gene. In two of those cases, the gene was found to have been altered, which apparently made it defective.

This association of a defective gene with an abnormal result supports evidence that the gene helps determine a person’s sex, the researchers said.

Two independent teams of European researchers reported their results in the British journal Nature in November. Discovery of the gene, called Sry, was announced in July along with some evidence of its sex-determining function.

Sry lies within the bundle of genes called the Y chromosome, usually inherited only by males.

The latest findings “provide fairly strong support for the role of Sry in sex determination,” Dr. David Page of the Whitehead Institute of Cambridge, Mass., said in a telephone interview.

The European scientists said they were unable to find any Sry mutation in most women they tested who carried the gene. In those cases, they suggested, a mutation may lie in a part of the gene that was not examined, or there may be a defect in some other gene that helps determine gender.