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.

Penn researchers identify first sex chromosome gene involved in meiosis and male infertility

A team of scientists led by University of Pennsylvania veterinary researchers have identified a gene, TEX11, located on the X chromosome, which when disrupted in mice renders the males sterile and reduces female fecundity.

17 Mar 2008

Genomic tool helps select best eggs for IVF

A research team supervised by Universite Laval scientist Marc-Andre Sirard has identified genetic markers that allow the selection of eggs with the best chance of leading to successful pregnancy after in vitro fertilization (IVF).

13 Mar 2008

New genetic finding on Rett syndrome

The first comprehensive analysis of the clinical effects of genetic mutations involved in Rett syndrome will enable affected families to receive a more accurate indication of their child's prognosis.

12 Mar 2008

Scientists characterizes novel regulator of chromosome function

The Stowers Institute's Workman Lab has shed new light on a novel histone acetyltransferase protein complex called ATAC.

11 Mar 2008

Colorectal cancer gene found

Case Western Reserve University School of Medicine researchers published a study in the March 7th issue of The American Journal of Human Genetics identifying the hereditary components of colorectal cancer (CRC.)

10 Mar 2008

Prader-Willi syndrome - new genetic clues

A new mouse model for a genetic cause of obesity has been developed by scientists at the Stanford University School of Medicine and Lucile Packard Children's Hospital.

6 Mar 2008

New genetic marker of risk for breast cancer discovered

An international group of investigators led by scientists at Memorial Sloan-Kettering Cancer Center (MSKCC) and the National Cancer Institute has identified a new genetic marker of risk for breast cancer.

4 Mar 2008

Genetic variations increase risk of anxiety disorders

Massachusetts General Hospital (MGH) researchers - in collaboration with scientists at the University of California at San Diego and Yale University - have discovered perhaps the strongest evidence yet linking variation in a particular gene with anxiety-related traits.

4 Mar 2008

Genetic mutation linked to peripheral artery disease

The finding, appearing online in the journal Circulation, is the first to document a genetic mutation linked to PAD. Although the work was done in mice, researchers say it is likely to give them new insight into how PAD develops and progresses in humans.

26 Feb 2008

Curcumin reduces heart enlargement and may prevent heart failure

Eating curcumin, a natural ingredient in the spice turmeric, may dramatically reduce the chance of developing heart failure, researchers at the Peter Munk Cardiac Centre of the Toronto General Hospital have discovered.

22 Feb 2008

Smoking's effects on genes may play a role in lung cancer development and survival

Smoking plays a role in lung cancer development, and now scientists have shown that smoking also affects the way genes are expressed, leading to alterations in cell division and regulation of immune response.

21 Feb 2008

Scientists reveal a new target to fight bad cholesterol

Scientists have uncovered a new region in the genome that is responsible for the body's ability to regulate bad cholesterol which is linked to heart attack and stroke.

8 Feb 2008

New approach to genetic diagnosis in autism

A practical, stepwise approach to diagnosing genetic causes of autism and related disorders is proposed in the January issue of Genetics in Medicine, official journal of the American College of Medical Genetics (ACMG), published by Lippincott Williams & Wilkins.

7 Feb 2008

Chemical chaperone could open door to treatment of neurological disorder

An unexpected finding turned out to be a clue leading researchers at Washington University School of Medicine in St. Louis to propose a new treatment approach for Niemann-Pick disease, a rare, deadly neurodegenerative disorder.

7 Feb 2008

Researchers identify cells that cause nervous system disease

Two teams of University of Michigan researchers have tracked down the cells responsible for neurofibromatosis type1, a disfiguring, incurable condition and one of the most common hereditary disorders.

4 Feb 2008

Researchers unravel mystery of cell division

Experts in mitosis (cell division) at the University of Virginia Health System have made discoveries that explain how one protein the kinase Aurora B could have such a large role in guiding and policing the process of cell division.

25 Jan 2008

Discovery of multiple genes linked to systemic lupus erythematosus

A landmark genetic study has identified multiple genes linked to systemic lupus erythematosus (SLE), or lupus, a debilitating autoimmune disease that affects an estimated 1.4 million Americans.

21 Jan 2008

Genome scan shows Polynesians and Micronesians have almost no genetic relation to Melanesians

The origins and current genetic relationships of Pacific Islanders have generated interest and controversy for many decades.

21 Jan 2008

Previously unknown chromosomal abnormalities play substantial role in autism

Genome-wide scans of families affected by autism spectrum disorder (ASD) have revealed new evidence that previously unknown chromosomal abnormalities have a substantial role in the prevalent developmental disorder, according to a report published online Jan. 17th in the American Journal of Human Genetics, a publication of Cell Press.

18 Jan 2008

Molecules might identify high-risk acute-leukemia patients

New research suggests that certain small molecules used by cells to control the proteins they make might also help doctors identify adult acute-leukemia patients who are likely to respond poorly to therapy.

16 Jan 2008