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.

World's deadliest malaria parasite cloaking gene revealed

The world's deadliest malaria parasite, Plasmodium falciparum, sneaks past the human immune system with the help of a wardrobe of invisibility cloaks. If a person's immune cells learn to recognize one of the parasite's many camouflage proteins, the surviving invaders can swap disguises and slip away again to cause more damage. Malaria kills an estimated 2.7 million people annually worldwide, 75 percent of them children in Africa.

29 Dec 2005

Chromosome link found between alcohol addiction and smoking

Scientists have found in a study of tobacco users that their drinking behavior is linked to some of the same chromosome regions associated with alcohol addiction.

22 Dec 2005

Scientists discover how HIV infects healthy cells

Using sophisticated detection methods, researchers at the Saint Louis University Institute for Molecular Virology (IMV) have demonstrated the molecular mechanism by which the HIV virus infects, or integrates, healthy cells. The discovery could lead to new drug treatments for HIV.

22 Dec 2005

Keep on trying - when you do get pregnant the chances are it will be a boy!

A team of Dutch researchers at Maastricht University say that women who take longer to get pregnant are more likely to give birth to a boy.

19 Dec 2005

Researchers discover potential mechanism for tumor growth

Researchers at Columbia University Medical Center have identified an inherent feature of stem and progenitor cells that may promote initiation and progression of cancerous tumors.

15 Dec 2005

AMN107 drug shows promise in leukemia resistance to Gleevec

The targeted agent AMN107 can produce dramatic benefits in patients with some forms of leukemia that are resistant to Gleevec, the standard therapy for these cancers, say researchers at The University of Texas M. D. Anderson Cancer Center.

13 Dec 2005

Securin is not required for chromosomal stability in human cells

A critical aspect of cell division, or mitosis, is that the progeny cells must receive the full complement of chromosomes.

13 Dec 2005

Importance of telomeres in preserving genome integrity and preventing cancer development

Researchers at the Salk Institute for Biological Studies discovered that cells co-opted the machinery that usually repairs broken strands of DNA to protect the integrity of chromosomes.

7 Dec 2005

Hippocampal myo-inositol and cognitive ability in adults with Down Syndrome

Researchers from the Institute of Psychiatry at King's College London have identified a molecule that could be targeted to treat the cognitive impairment in people with Down syndrome.

7 Dec 2005

Disruption of normal gene interaction linked to schizophrenia

Disruption of the normal interaction between the genes PRODH and COMT contributes directly to major symptoms of schizophrenia by upsetting the balance of the brain chemicals glutamate and dopamine, according to a group of investigators that includes a scientist now at St. Jude Children's Research Hospital.

2 Dec 2005

Study links low level of response (LR) to alcohol to an area on chromosome 10

How a person "feels" the effects of alcohol is, in part, genetically influenced and relates to their risk for developing alcoholism.

28 Nov 2005

Analysis of Fcg Receptor haplotypes in rheumatoid arthritis

People with a specific combination of variants of two genes, encoding two different receptors for the antibody Fc gamma, are three times more likely to develop rheumatoid arthritis than individuals with different variant combinations.

28 Nov 2005

Loss of genes on chromosome 1 or 11 raises the risk of death from the children's cancer neuroblastoma

A new study reports that a loss of genes on chromosome 1 or chromosome 11 raises the risk of death from the children's cancer neuroblastoma, even when other indicators seem to point to a lower-risk form of the disease.

28 Nov 2005

Fc gamma receptor gene variants associated with rheumatoid arthritis

10 Nov 2005

Genetic link to dyslexia

About five million Germans have serious learning difficulties when it comes to reading and writing. It is frequently the case that several members of the same family are affected. So hereditary disposition seems to play an important role in the occurrence of dyslexia.

7 Nov 2005

DCDC2 gene linked to dyslexia

Pediatric researchers at Yale School of Medicine have identified a gene on human chromosome 6 called DCDC2, which is linked to dyslexia, a reading disability affecting millions of children and adults.

30 Oct 2005

Mechanisms of evolution may be associated with disease

By comparing the human genome with that of the chimpanzee, man's closest living relative, researchers have discovered that chunks of similar DNA that have been flipped in orientation and reinserted into chromosomes are hundreds of times more common in primates than previously thought.

26 Oct 2005