X chromosome


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Related to X chromosome: Y chromosome

X chromosome

[′eks ′krō·mə‚sōm]
(genetics)
The sex chromosome occurring in double dose in the homogametic female sex and in single dose in the heterogametic male sex in mammals, Diosophila, and many other organisms.
References in periodicals archive ?
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 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.
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 genes.
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.