If this holds true, they could be under the influence of the same mysterious
X chromosome factor as the mice.
Since women have two
X chromosomes, the mothers had a backup copy of a normal neuroligin gene that presumably protected them from developing autism.
They found that, unlike in mouse placental cells, Tsix is expressed only on the inactive
X chromosome and is thus unlikely to be stopping Xist.
(In contrast, male fruit flies double the activity of their single
X chromosome.)
It then directed most of those bearing
X chromosomes to swim down one collection tube, and most of the Y-bearing sperm went down another tube.
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 inactivation.
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.37).
Because if you're female, no matter what you do to your limbs and outward flourishes, you'll still have two
X chromosomes. If male, an X and a Y.
Unfertilized fish eggs normally carry one of the mother's two
X chromosomes. Sperm can carry either the father's X or his Y chromosome.
In at least eight species of the mouse genus Akodon, from 10 percent to 60 percent of the females carry a Y chromosome in place of one of the two
X chromosomes usually found in the cells of female mammals, report Hopi E.
