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.

How DNA repair machinery detects and corrects errors in DNA replication

Biochemists at Duke University Medical Center have discovered key components that enable the cell's DNA repair machinery to adeptly launch its action in either direction along a DNA strand to strip out faulty DNA.

2 Jul 2004

Chromosomal chaos in early embryonic development is linked to abnormalities in cytokinesis and spindle formation

Abnormalities in the spindles (the bi-polar thread like structures that link and pull the chromosomes during cell division) of human embryos before implantation may be the primary reason for many of the chromosome defects observed in early human development

29 Jun 2004

A moderately high protein diet could reduce a woman’s chances of becoming pregnant

A moderately high protein diet could reduce a woman’s chances of becoming pregnant, according to new research presented at the 20th annual conference of the European Society of Human Reproduction and Embryology today on Monday 28 June.

28 Jun 2004

Discovery of gene that causes a rare juvenile-onset form of amyotrophic lateral sclerosis (ALS)

The discovery of the Senataxin gene, on chromosome 9q34, may provide clues to the mechanisms of related brain disorders. The study appears in the June 2004 issue of the American Journal of Human Genetics.

28 Jun 2004

Catalogue of the 30,000 or so genes that contain the instructions to make a human or a mouse

With genomic sequencing at The Wellcome Trust Sanger Institute and other centres, researchers now have an extensive catalogue of the 30,000 or so genes that contain the instructions to make a human or a mouse.

24 Jun 2004

New gene found in genetic wasteland

In a region of DNA long considered a genetic wasteland, Harvard Medical School researchers have discovered a new class of gene.

20 Jun 2004

Geneticists determine the lack of chromosomes

A healthy person’s genome contains 46 chromosomes, but an individual cell can contain less. Contemporary methods allow to determine the value of losses rather accurately. The Tomsk researchers’ effort has been supported by the Russian Foundation for Basic Research.

15 Jun 2004

Significance of the discovery of anthrax toxin genes in a naturally occurring microbe other than Bacillus anthracis

Dr. Fraser discusses, for the first time, the significance of the discovery of anthrax toxin genes in a naturally occurring microbe other than Bacillus anthracis, the bacterium that causes anthrax.

14 Jun 2004

Breakthrough in gene therapy

Despite a roller-coaster ride of ups and downs during the past 15 years, gene therapy has continued to attract many of the world's brightest scientists. They are tantalized by the enormous potential that replacing missing genes or disabling defective ones offers for curing diseases of many kinds.

3 Jun 2004

How we pass our genes to our children

An Oxford-led team of researchers has found out more about what happens during recombination, the process by which the genetic information you inherited from your mother and father is mixed up to make a sex chromosome to pass on to your offspring.

1 Jun 2004

Evidence that abnormally short telomeres play a role in the early development of cancer

Scientists at the Johns Hopkins Kimmel Cancer Center say they have evidence that abnormally short telomeres - the end-caps on chromosomes that normally preserve genetic integrity -appear to play a role in the early development of many types of cancer.

27 May 2004

Researchers have identified the first gene linked to the productivity of the stem cells that produce sperm in mammals

Researchers have identified the first gene linked to the productivity of the stem cells that produce sperm in mammals. The discovery was made by applying the latest laboratory methods to a strain of mice restored from embryos frozen since the early 70s.

23 May 2004

Genome research sheds light on Bardet-Biedl syndrome

By comparing the genomes of an alga, a weed and humans, a team of researchers has identified a new gene behind Bardet-Biedl syndrome (BBS), a complex condition marked by learning disabilities, vision loss and obesity.

21 May 2004

Scientists believe that the dog genome holds a wealth of information that will benefit human health

Recently completed genetic analysis reveals that half of the more than 300 inherited canine disorders — including a number of cancers — resemble specific diseases of man; many scientists believe that the dog genome holds a wealth of information that will benefit human health.

20 May 2004

Discovery of the gene for Cornelia de Lange syndrome

An international team of researchers has discovered the gene for Cornelia de Lange syndrome, a disabling, multisystem genetic disease that affects an estimated one in 10,000 children. The finding is expected to lead to a genetic test, enabling rapid and definitive diagnosis of the syndrome, as well as prenatal testing for families who already have one child with the disease.

17 May 2004

Want a new type of man? Maybe less brawn and more brains?

A new version of the human male is a distinct possibility, given the genetic erosion of the “junk” sex-determining chromosome that makes men male.

17 May 2004

Chromosome losses can signal an especially poor response to therapy

A new international study of children with a severe form of acute lymphoblastic leukemia(ALL) shows that certain chromosome losses can signal an especially poor response to therapy, but that other chromosome abnormalities have no effect on treatment survival.

13 May 2004

New way by which cells can become cancerous may solve mystery with lung cancer

Researchers at The University of Texas M. D. Anderson Cancer Center are describing an entirely new way by which cells can become cancerous. And they say their finding provides an answer to a mystery in lung and other cancers.

8 May 2004

Researchers find an entirely new way by which cells can become cancerous

Finding provides an answer to a mystery in lung and other cancers: why a potent tumor suppressor gene called FUS1 functions as it should, yet none of the protein it produces can be found anywhere in a cancer cell.

6 May 2004

Study sheds new light on children with a severe form of acute lymphoblastic leukemia

A new international study of children with a severe form of acute lymphoblastic leukemia (ALL) shows that certain chromosome losses can signal an especially poor response to therapy, but that other chromosome abnormalities have no effect on treatment survival.

5 May 2004