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.

Discovery of novel genetic markers linked to increased risk of heart attack

An international team of researchers including scientists of Helmholtz Zentrum München has succeeded in identifying new gene variants associated with an increased risk for myocardial infarction (MI), or heart attack.

17 Feb 2009

2 genes influence social behavior, visual-spatial performance in people with Williams syndrome

Unraveling the genetics of social behavior and cognitive abilities, researchers at the University of Utah and the Salk Institute for Biological Studies have traced the role of two genes,GTF2I and GTF2IRD, in a rare genetic disorder known as Williams Syndrome.

11 Feb 2009

Micro RNA plays a key role in melanoma metastasis

Scientists have long wondered how melanoma cells travel from primary tumors on the surface of the skin to the brain, liver and lungs, where they become more aggressive, resistant to therapy, and deadly.

9 Feb 2009

Lack of specific gene plays role in autism

It is estimated that three to six out of every 1,000 children in the United States have autism - and the number of diagnosed cases is rising.

9 Feb 2009

Missing gene plays role in autism

It is estimated that three to six out of every 1,000 children in the United States have autism - and the number of diagnosed cases is rising.

8 Feb 2009

Discovery of direct link between vitamin D and MS susceptibility 'gene'

Researchers have found evidence that a direct interaction between vitamin D and a common genetic variant alters the risk of developing multiple sclerosis (MS).

8 Feb 2009

Guidance for evaluating menopause-like condition in girls and young women

A comprehensive plan to help health care professionals diagnose and treat primary ovarian insufficiency-a menopause-like condition affecting girls and young women that may occur years before normal menopause is expected-has been developed by a scientist at the National Institutes of Health.

5 Feb 2009

Discovery of new schizophrenia gene

Researchers at the Johns Hopkins University School of Medicine are one gene closer to understanding schizophrenia and related disorders.

3 Feb 2009

Sociability traced to region of brain called amygdala

People with a genetic condition called Williams syndrome are famously gregarious. Scientists, looking carefully at brain function in individuals with Williams syndrome, think they may know why this is so.

29 Jan 2009

Breakthrough in prenatal screening for Down syndrome

Lenetix, Inc. today announced a significant step in the development of an improved first and second trimester non-invasive fetal chromosomal screening test to detect Down syndrome and other genetic fetal conditions.

29 Jan 2009

Scientists explain genetic disease first discovered in Quebec 24 years ago

Scientists at the MUHC and McGill University have identified a gene essential for the uptake of vitamin B12 in human cells.

15 Jan 2009

Discovery of link between genetic defect on chromosome 15 and epilepsy

In a research published in the advanced online publication of the scientific magazine Nature Genetics, researchers have identified a genetic defect for common epilepsies on chromosome 15.

15 Jan 2009

Discovery of first gender-linked susceptibility gene for late-onset Alzheimer's disease

In the Jan. 11 online edition of Nature Genetics, they report the results of their two-stage genome-wide association study of patients with Alzheimer's disease. The research showed that women who inherited two copies of a variant in the PCDH11X gene, found on the X chromosome, are at considerably greater risk of developing Alzheimer's disease.

12 Jan 2009

Missing DNA the culprit in epilepsy?

An international team of scientists have identified a genetic risk factor for epilepsy which may lead to a better understanding of what causes the seizures and the development of new treatments for the condition.

12 Jan 2009

New genetic markers for ulcerative colitis could lead to treatment

An international consortium of researchers, including major contribution from a team led by Dr. John D. Rioux, a professor of medicine at the Université de Montréal and the Montreal Heart Institute, has identified genetic markers associated with risk for ulcerative colitis.

8 Jan 2009

New drug being tested for Fragile X syndrome

A pilot trial of an oral drug therapy called fenobam has shown promising initial results and could be a potential new treatment option for adult patients with Fragile X syndrome (FXS).

6 Jan 2009

Metadherin gene linked to metastasis of breast cancer

A team of researchers at Princeton University and The Cancer Institute of New Jersey has identified a long-sought gene that is fatefully switched on in 30 to 40 percent of all breast cancer patients, spreading the disease, resisting traditional chemotherapies and eventually leading to death.

5 Jan 2009

Discovery of new syndrome associated with severe congenital neutropenia

A team of scientists has discovered a new syndrome associated with severe congenital neutropenia (SCN), a rare disorder in which children lack sufficient infection-fighting white cells, and identified the genetic cause of the syndrome: mutations in the gene Glucose-6-phosphatase, catalytic subunit 3 (G6PC3).

5 Jan 2009

Discovery of new genetic markers for ulcerative colitis

An international team led by University of Pittsburgh School of Medicine researchers has identified genetic markers associated with risk for ulcerative colitis.

5 Jan 2009

Neuropeptide Y gene variation may lead to early coronary artery disease

Researchers from Duke University Medical Center have identified a variation in a particular gene that increases susceptibility to early coronary artery disease.

5 Jan 2009