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.

Dopamine link to psychiatric and neurological disorders

A gene that regulates dopamine levels in the brain is involved in the development of schizophrenia in children at high risk for the disorder, say researchers at the Stanford University School of Medicine, Lucile Packard Children's Hospital and the University of Geneva.

23 Oct 2005

Gene found only in men is altered by a chemical process, which is in turn linked to aggressive forms of melanoma

New scientific evidence that may shed light on why men are more likely than women to develop aggressive forms of skin cancer has been published in Carcinogenesis.

23 Oct 2005

Identification of a single chromosome region linked to specific language impairment

Researchers at the University of Toronto (U of T), Capital Health's Stollery Children's Hospital in Edmonton, Toronto's Hospital for Sick Children and their international collaborators have discovered a genetic abnormality that causes a type of language impairment in children

19 Oct 2005

Significant step forward in the genome era

In what promises to be a significant step forward in the genome era, the National Human Genome Research Institute (NHGRI) today announced plans to devote a portion of its large-scale sequencing capacity to efforts aimed at identifying the genetic roots of specific diseases that have long eluded gene hunters.

17 Oct 2005

Tourette syndrome linked to SLITRK1 gene

Tourette syndrome is a distressing condition which affects one in every 100 people.

17 Oct 2005

PCBs found widely in the environment and absorbed in the diet - may damage sperm

Research by an European Union-supported international team of scientists has shown that polychlorinated biphenyls (PCBs) - synthetic organic chemicals found widely in the environment and absorbed in the diet - may damage sperm.

13 Oct 2005

First gene mutation associated with Tourette syndrome

Researchers have identified the first gene mutation associated with Tourette syndrome - opening a new avenue for understanding the complex disorder that causes muscle and vocal tics.

13 Oct 2005

Chromosomes in the nucleus of the cell carry the material of heredity, or genes

Abnormal cell division that yields cells with an extra set of chromosomes can initiate the development of tumors in mice, researchers at Dana-Farber Cancer Institute have shown, validating a controversial theory about cancer causation put forth by a scientific visionary nearly 100 years ago.

12 Oct 2005

Specific gene on chromosome 15 regulates inflammation

A team of international researchers has discovered that a specific gene on chromosome 15 regulates inflammation, a finding with implications for a wide range of disorders, including cancer, cardiovascular disease, diabetes, obesity, Alzheimer's, and infections. The findings are published in the October 9 online issue of Nature Genetics.

9 Oct 2005

Tissue engineering used to reconstruct defective tracheas (windpipes) in fetal lambs

Researchers at Children's Hospital Boston report using tissue engineering to reconstruct defective tracheas (windpipes) in fetal lambs, first using cells from the amniotic fluid to grow sections of cartilage tube, and then implanting these living grafts into the lambs while still in the womb.

9 Oct 2005

New information regarding the genetic, cellular and neurological bases of susceptibility to autism and schizophrenia

Two New Jersey research teams are reporting discoveries about the biological nature of psychiatric disorders that may bring them closer to the ultimate goal of finding cures for complex diseases, such as autism and schizophrenia.

9 Oct 2005

Researchers identify gene defect in mice that causes cyclical hair loss and skin cancer

Researchers at Jefferson Medical College and at the Wadsworth Center in New York have identified a gene defect in mice resulting in a range of abnormalities, from cyclical hair loss and skin cancer to severe problems in normal skin development.

4 Oct 2005

Mechanism of X-chromosome dosage compensation in Drosophila

In Drosophila, like in humans, male cells have a single X chromosome, while female cells have two. Researchers have long debated over how X and autosomal chromosome gene expression is equalized between the sexes (generally regarding two different models, known as the activation model and the inverse model).

4 Oct 2005

Research on cartilage erosion and bone abnormalities

While characteristic of osteoarthritis (OA), a degenerative joint disease that affects some 20 million Americans, cartilage erosion and bone abnormalities are also associated with many rare hereditary conditions.

3 Oct 2005

Discovery establishes a role for the gene Rsf-1 in ovarian cancer

Johns Hopkins Kimmel Cancer Center researchers have linked alterations in a gene, called Rsf-1, to the most deadly ovarian cancers. The scientists say the discovery is the first to establish a role for the gene in ovarian cancer and may lead to a test that can predict, early on, which patients will develop aggressive disease.

3 Oct 2005

Discovered of gene mutations associated with hereditary neuralgic amyotrophy

In a significant advance toward understanding a perplexing and painful neurological disorder, an international team of researchers has discovered gene mutations associated with an inherited chronic pain and weakness syndrome known as hereditary neuralgic amyotrophy (also called HNA).

27 Sep 2005

Gene responsible for Neuralgic Amyotrophy identified

Neuralgic Amyotrophy is a painful disorder of the peripheral nervous system. This heritable disease causes prolonged acute attacks of pain in the shoulder or arm, followed by temporary paralysis.

27 Sep 2005

Researchers map genetic location that explains why certain blood pressure-lowering drugs aren't effective for some people

"The findings bring us a step closer to developing targeted therapies for patients with high blood pressure who might otherwise be started on medications that won't help," said lead author Sandosh Padmanabhan, Ph.D.

26 Sep 2005

Mutations in the gene, called PIG-A may help identify individuals at high risk for cancer

A new study to detect an elevated rate of mutations in a gene on the X chromosome holds promise for developing a test that could identify individuals at risk for developing cancer.

26 Sep 2005

Definitive multiple sclerosis linkage screen

A cluster of genes on chromosome six is the only one that plays a significant role in multiple sclerosis (MS), according to the most complete genetic study to date in the disorder, presented at the 130th annual meeting of the American Neurological Association in San Diego.

22 Sep 2005

Chromosome X News and Research

Further Reading

Dopamine link to psychiatric and neurological disorders

Gene found only in men is altered by a chemical process, which is in turn linked to aggressive forms of melanoma

Identification of a single chromosome region linked to specific language impairment

Significant step forward in the genome era

Tourette syndrome linked to SLITRK1 gene

PCBs found widely in the environment and absorbed in the diet - may damage sperm

First gene mutation associated with Tourette syndrome

Chromosomes in the nucleus of the cell carry the material of heredity, or genes

Specific gene on chromosome 15 regulates inflammation

Tissue engineering used to reconstruct defective tracheas (windpipes) in fetal lambs

New information regarding the genetic, cellular and neurological bases of susceptibility to autism and schizophrenia

Researchers identify gene defect in mice that causes cyclical hair loss and skin cancer

Mechanism of X-chromosome dosage compensation in Drosophila

Research on cartilage erosion and bone abnormalities

Discovery establishes a role for the gene Rsf-1 in ovarian cancer

Discovered of gene mutations associated with hereditary neuralgic amyotrophy

Gene responsible for Neuralgic Amyotrophy identified

Researchers map genetic location that explains why certain blood pressure-lowering drugs aren't effective for some people

Mutations in the gene, called PIG-A may help identify individuals at high risk for cancer

Definitive multiple sclerosis linkage screen

Achieving and maintaining ISO/IEC 27001 and BS 10012 certifications

Expanding research and clinical options for children with cancer

Examining how pain could play a direct protective role in the gut

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