Although many boys will start puberty normally, the extra X chromosome
interferes with the body's ability to produce testosterone.
These results indicate that there may be an undiscovered gene on the X chromosome
that affects sexual behaviours in mice and perhaps in other mammals, the researchers say.
The reason is that women can often compensate for a defective X chromosome
gene if the counterpart gene on their second X chromosome
is in working order.
In a female embryo, the choice of which X chromosome
to inactivate--either that from the mother or that from the father--is random in each cell.
In contrast, male fruit flies double the activity of their single X chromosome
The researchers divided their volun-teers into two groups: 55 with a complete X chromosome
inherited from their mother and 25 with an undamaged X chromosome
from their father.
Two new reports add to a growing body of evidence that an unusual gene called Xist may hold the key to X chromosome
Page and his colleagues suggest that this finding is at odds with theories that the Y chromosome, once it started evolving separately from the X chromosome
, only degenerated.
Two years ago, Hamer reported that men might inherit a predisposition to homosexuality through the X chromosome
, whose genes are passed on by mothers (SN: 7/17/93, p.
Although researchers are still not sure exactly why this occurs, many assert that X inactivation initially arose to prevent the genetic inequity that would result if females had a double dose of active X chromosome
Men have one X chromosome
and one male-determining Y chromosome, while women have two X chromosomes
An uncommon form of manic depression may be linked to markers on the X chromosome
, the NIMH scientists say in the April ARCHIVES OF GENERAL PSYCHIATRY.