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.

Rheumatoid arthritis genes

A paper published this week in the open access journal PLoS Medicine provides strong evidence that one specific part of the genome is associated with rheumatoid arthritis.

18 Sep 2007

Gene profiling can single out the worst cases of multiple myeloma and guide therapy

Multiple myeloma patients vary widely in how they respond to treatment, but now researchers at the Myeloma Institute for Research and Therapy at the University of Arkansas for Medical Sciences have identified a small subset of genes whose activity could predict high-risk cases and potentially guide therapy in the future.

18 Sep 2007

Chronic stress can steal years from caregivers' lifetimes

The chronic stress that spouses and children develop while caring for Alzheimer's disease patients may shorten the caregivers' lives by as much as four to eight years, a new study suggests.

18 Sep 2007

New understanding of gene mutation responsible for fragile X syndrome

Scientists have discovered how the gene mutation responsible for fragile X syndrome - the most common inherited form of mental retardation - alters the way brain cells communicate.

18 Sep 2007

New insight into the mechanisms of Lou Gehrig's disease

There is no known cure for amyotrophic lateral sclerosis (ALS), often known as Lou Gehrig disease and motor neuron disease.

13 Sep 2007

Unique role for blood formation gene MLL identified

All blood cell production in adults depends on the steady work of a vital gene that if lost results in early bone marrow failure, Dartmouth Medical School cancer geneticists have found.

13 Sep 2007

Ultraconserved non-coding RNAs may be important in human cancer

Research here shows that an obscure form of RNA, part of the protein-making machinery in all cells, might play an important role in human cancer.

12 Sep 2007

New genetic risk factor for rheumatoid arthritis and lupus

A genetic variation has been identified that increases the risk of two chronic, autoimmune inflammatory diseases: rheumatoid arthritis (RA) and systemic lupus erythematosus (lupus).

10 Sep 2007

Congestive heart failure is rare among leukemia patients who take imatinib

Congestive heart failure rarely occurs among leukemia patients who take imatinib, researchers at The University of Texas M. D. Anderson Cancer Center found after an exhaustive review of the detailed medical histories of 1,276 patients who enrolled in clinical trials for the drug.

10 Sep 2007

First individual genome sequence of one person

Independent sequence and assembly of the six billion base pairs from the genome of one person ushers in the era of individualized genomics

4 Sep 2007

Discovery suggests location of genes for breast density, a strong risk factor for breast cancer

Studying the DNA of 889 people, gene hunters at the Mayo Clinic and H. Lee Moffitt Cancer Centers have identified a region on chromosome 5p that is significantly associated with dense breast tissue, a known risk factor for breast cancer.

2 Sep 2007

One species' entire genome discovered inside another's

Scientists at the University of Rochester and the J. Craig Venter Institute have discovered a copy of the entire genome of a bacterial parasite residing inside the genome of its host species.

30 Aug 2007

Researchers dispute immortal strand hypothesis

How do adult stem cells protect themselves from accumulating genetic mutations that can lead to cancer?

30 Aug 2007

Genetics of imatinib resistance in acute lymphoblastic leukemia

In the September 15th issue of Genes & Development, Drs. Richard T. Williams, Willem den Besten, and Charles J. Sherr at Howard Hughes Medical Institute, St. Jude Children's Research Hospital in Memphis TN, lend new insights into how an aggressive form of acute lymphoblastic leukemia (ALL) develops, and how sensitivity to the targeted chemotherapeutic drug, imatinib, can be diminished through interactions between tumor cells and the host microenvironment.

30 Aug 2007

1,000 strains of mice that feature the genetic diversity of the world population

Mice that are part of the Collaborative Cross project at Oak Ridge National Laboratory are helping scientists around the world learn more about possible causes of drug abuse, diabetes, sleep disorders, stress and pain, kidney disease and a number of other conditions that affect millions of people.

30 Aug 2007

Fingolimod shows promise in 2 lethal leukemias

A new study suggests that an experimental drug being tested for the treatment of multiple sclerosis and to prevent organ rejection might also help people with certain deadly forms of chronic and acute leukemia.

29 Aug 2007

St. Jude discovers factors that accelerate resistance to Gleevec targeted therapy in lymphoblastic leukemia

Results of a study by investigators at St. Jude Children's Research Hospital provide strong evidence for why the drug imatinib (Gleevec), which has revolutionized the treatment of chronic myelogenous leukemia (CML), is often unable to prevent relapse of a particularly aggressive form of acute lymphoblastic leukemia (ALL).

29 Aug 2007