X chromosome

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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The second model would reveal how an extra X chromosome affected the male mice.
Autism appears in four times as many men as women, so scientists have long suspected that the X chromosome contains relevant genes.
A gene that scientists have found to regulate X chromosome activity in mice doesn't work in people, report researchers from the Johns Hopkins Medical Institutions in Baltimore.
These bits of RNA have a thing for X chromosomes. At the appropriate time in development, they appear to coat the entire length of one of the X chromosomes, which then condenses into a Barr body.
When the researchers analyzed the sperm in the X collection tube, they found that 85 percent had the X chromosome, as desired.
Both groups of volunteers achieved lower scores on those measures than previously established standards for females with two complete X chromosomes, the researchers note.
This result, also published in the March 20 Nature, strongly implies that cells tally their X chromosomes by simply counting Xist genes, says Ashworth.
In another test, which Hamer had been chastised for not doing in the 1993 study, investigators examined the X chromosomes of heterosexual brothers of the homosexual men.
In the 1960s, geneticists discovered that female mammalian embryos randomly inactivate one of their X chromosomes. 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.
In theory, because his mother's X chromosomes carried no hemophilia genes, the boy had no chance of being born a hemophiliac.
The fetal cells are then tested to determine if they contain an extra X chromosome. The genetic counselor explained that girls with Trisomy X often have speech delays in early childhood, may be slower to walk and develop motor skills, and frequently have learning disabilities.
"Today, the human Y chromosome contains less than 200 genes, while the human X chromosome contains around 1,100 genes," said Wilson.