Chromosome X News and Research

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The X chromosome is one of the two sex chromosomes in humans (the other is the Y chromosome). The sex chromosomes form one of the 23 pairs of human chromosomes in each cell. The X chromosome spans about 155 million base pairs (the building blocks of DNA) and represents approximately 5 percent of the total DNA in cells.

Each person normally has one pair of sex chromosomes in each cell. Females have two X chromosomes, while males have one X and one Y chromosome. Early in embryonic development in females, one of the two X chromosomes is randomly and permanently inactivated in somatic cells (cells other than egg and sperm cells). This phenomenon is called X-inactivation or Lyonization. X-inactivation ensures that females, like males, have one functional copy of the X chromosome in each body cell. Because X-inactivation is random, in normal females the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells.

Some genes on the X chromosome escape X-inactivation. These genes are located at the tip of the short (p) arm of the X chromosome in an area known as the pseudoautosomal region. Although many genes are unique to the X or Y chromosome, genes in the pseudoautosomal region are present on both chromosomes. As a result, men and women each have two functional copies of these genes. Many genes in the pseudoautosomal region are essential for normal development.

Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. The X chromosome likely contains between 900 and 1,400 genes.

Genes on the X chromosome are among the estimated 20,000 to 25,000 total genes in the human genome.

Researchers associate six new genetic variants with heart disease risk factor

Using new techniques for rapidly scanning the human genome, researchers have associated levels of cholesterol and triglycerides, two fats in the blood, to 18 genetic variants, six of which represent new DNA regions never before associated with the traits.

15 Jan 2008

U.S. Food and Drug Administration approves new genetic breast cancer test

The U.S. Food and Drug Administration has approved a test that helps in assessing the risk of tumor recurrence and long-term survival for patients with relatively high-risk breast cancer. The TOP2A FISH pharmDx is the first approved device to test for the TOP2A (topoisomerase 2 alpha) gene in cancer patients.

14 Jan 2008

Discovery of gene variant that raises autism risk

Scientists have found a variation in a gene that may raise the risk of developing autism, especially when the variant is inherited from mothers rather than fathers.

11 Jan 2008

RNA silences cancer suppressor gene

One way cancer arises is when tumor suppressor genes that normally keep cell growth in check are mysteriously turned off.

10 Jan 2008

Discovery of chromosomal abnormality that appears to increase susceptibility to autism

A multi-institutional study involving Massachusetts General Hospital (MGH) researchers has identified a chromosomal abnormality that appears to increase susceptibility to autism.

10 Jan 2008

Evolution of the sexes: What a fungus can tell us

Fungi don't exactly come in boy and girl varieties, but they do have sex differences.

10 Jan 2008

New research links autism to genetic disorder

New research from the United States suggests that autism may be caused by a genetic disorder.

10 Jan 2008

Discovery of a core mechanism underlying Fragile X syndrome

Researchers at UT Southwestern Medical Center are uncovering how brain cells are affected in Fragile X syndrome, the most common cause of inherited mental retardation and the most common genetic cause of autism.

9 Jan 2008

New understanding on the mechanics of gene transcription

The molecular machinery behind gene transcription -- the intricate transfer of information from a segment of DNA to a corresponding strand of messenger RNA -- isn't stationed in special "transcription factories" within a cell nucleus, according to Cornell researchers.

9 Jan 2008

Loss of a small portion of chromosome 16 linked to autism

Loss of a small portion of chromosome 16, known as 16p11.2, is significantly associated with autism report researchers from the University of Chicago Medical Center, the University of Illinois at Chicago, and the Roswell Park Cancer Institute in an article, published Dec. 21, 2007, online by the journal Human Molecular Genetics.

9 Jan 2008

Comprehensive gene atlas underlying drug addiction

Using an integrative meta-analysis approach, researchers from the Center for Bioinformatics at Peking University in Beijing have assembled the most comprehensive gene atlas underlying drug addiction and identified five molecular pathways common to four different addictive drugs.

7 Jan 2008

Down syndrome points to a new way of repressing cancer growth

Researchers at Johns Hopkins and Ohio State University have found that the number of copies of a particular gene can affect the severity of colon cancer in a mouse model. Publishing in the Jan. 3 issue of Nature, the research team describes how trisomy 21, or Down syndrome in humans, can repress tumor growth.

4 Jan 2008

Down's syndrome gene protects against cancer

Researchers in the United States say the chromosomal abnormality that affects people with Down's syndrome also protects them against cancer.

3 Jan 2008

Scientists identifiy elusive telomere RNA subunit in single cell model

The Stowers Institute's Baumann Lab has identified the long-sought telomerase RNA gene in a single-cell research model.

28 Dec 2007

Tweaking a gene may fix Fragile X syndrome

According to new research clues to Fragile X syndrome may be connected to one single human gene.

20 Dec 2007

Discovery of new ALS gene

The ALS research team at Umea University in Sweden, working with Dutch and Belgian colleagues, has found new connections between mutations in gene DPP6 and contracting the non-hereditary form of ALS. The findings are being published december 16 in Nature Genetics on the Web.

18 Dec 2007

Genetic cause of Kawasaki disease

Researchers from Japan's RIKEN SNP Research Center, collaborating with a team at the University of California, San Diego (UCSD), have discovered a new genetic variation that affects a child's risk of getting Kawasaki disease (KD), an illness characterized by acute inflammation of the arteries throughout the body.

17 Dec 2007

Herceptin helps women with multiple chromosomes containing HER2 gene

The targeted therapy Herceptin helps women with HER2+ type of breast cancer independent of whether patients have extra copies of chromosome 17, home to the HER2 gene which produces the HER2 protein that fuels cancer growth.

17 Dec 2007

Same genetic machinery generates skin color evolution in fish and humans

When humans began to migrate out of Africa about 100,000 years ago, their skin color gradually changed to adapt to their new environments.

14 Dec 2007

Researchers advance stem cell gene therapy

Ireland Cancer Center of University Hospitals Case Medical Center researchers have recently made great strides in stem cell gene therapy research by transferring a new gene to cancer patients, via their own stem cells, with the ultimate goal of being able to use stronger chemotherapy treatment with less severe side effects.

13 Dec 2007