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.

Move over, Y chromosome - it's time X got some attention

In the first evolutionary study of the chromosome associated with being female, University of California, Berkeley, biologist Doris Bachtrog and her colleagues show that the history of the X chromosome is every bit as interesting as the much-studied, male-determining Y chromosome, and offers important clues to the origins and benefits of sexual reproduction.

16 Apr 2009

Discovery of gene variation linked to increased risk of ischemic stroke

Millions of people have a genetic variant linked to increased risk of ischemic stroke, reports an international research team including scientists at The University of Texas Health Science Center at Houston in a study published online by The New England Journal of Medicine on April 15.

15 Apr 2009

Discovery of potential genetic predisposition for lung cancer

University of Cincinnati (UC) cancer cell biologists have identified a distinct gene linked to increased lung cancer susceptibility and development.

15 Apr 2009

African sleeping sickness parasite breaks its own DNA to avoid detection

The parasite Trypanosoma brucei, which causes African sleeping sickness, is like a thief donning a disguise.

15 Apr 2009

Small RNAs can play critical roles in male infertility/contraception

University of Nevada School of Medicine scientists in the Department of Physiology and Cell Biology have discovered insight into the reproductive workings of the male sex chromosome that may have significant implications for male infertility and contraception.

12 Apr 2009

New genetic understanding of progressive hearing loss

In parallel studies in human and mouse, two groups of researchers have come to the same conclusion: that a new kind of gene is associated with progressive hearing loss.

12 Apr 2009

Gene fusion discovery may lead to improved prostate cancer test

A newly discovered gene fusion is highly expressed in a subset of prostate cancers, according to a study by researchers at Weill Cornell Medical College.

12 Apr 2009

Researchers explain process by which cells 'hide' potentially dangerous DNA segments

The DNA in the 23 pairs of chromosomes in each of the billions of cells of the human body is so tightly packed that it would measure six feet in length if stretched end to end.

12 Apr 2009

Multifocal lung cancers appear to originate from single cancer clone

Multiple, anatomically distinct lung cancer tumors may frequently arise from a single cancer cell, according to a retrospective analysis of patient tumor samples published in the April 7 online issue of the Journal of the National Cancer Institute.

8 Apr 2009

Discovery of gene variant associated with increased risk of atopic dermatitis

Scientists of the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch and Charité - University Medical School, Berlin, Germany, in collaboration with researchers from the Klinikum rechts der Isar of Technical University Munich and Christian Albrecht University, Kiel, have identified a gene variant on chromosome 11 that is associated with an increased risk of atopic dermatitis.

6 Apr 2009

Molecular test for cancer relapse in UK children

A molecular marker used in America to predict whether children with a form of kidney cancer, called Wilms' tumour, are more likely to relapse than other children, could be useful for UK patients.

2 Apr 2009

Researchers develop mouse models of leukemia that predict response to chemotherapy

Being able to accurately predict how a given cancer will respond to chemotherapy would spare patients with non-responsive tumors the burden of undergoing toxic and ultimately unhelpful treatment.

1 Apr 2009

Gene linked to lupus might explain gender difference in disease risk

In an international human genetic study, researchers at UT Southwestern Medical Center have identified a gene linked to the autoimmune disease lupus, and its location on the X chromosome might help explain why females are 10 times more susceptible to the disease than males.

30 Mar 2009

Gene linked to lupus might explain why females are 10 times more susceptible to the disease

30 Mar 2009

Discovery of new cancer gene

Researchers have identified a new cancer gene - one that is common to many cancers and affects the most basic regulation of our genes.

29 Mar 2009

'Gene hunters' find two new breast cancer genes

Cancer Research UK scientists have found two new regions of the genome that alter a woman's risk of breast cancer, according to a study in Nature Genetics.

29 Mar 2009

Evolutionary origin of bacterial chromosomes revealed

Researchers have unveiled the evolutionary origin of the different chromosomal architectures found in three species of Agrobacterium.

29 Mar 2009

Researchers identify genetic machinery responsible for synthesizing thiostrepton

Researchers at the Georgia Institute of Technology have identified the genetic machinery responsible for synthesizing thiostrepton, a powerful antibiotic produced by certain bacteria.

23 Mar 2009

Discovery of genetic link to blood cancers

The study, published in the journal Nature Genetics, has shown that susceptibility to a series of blood cancers, known as myeloproliferative disorders (MPDs), is linked to a particular area of the patient's DNA, which is prone to developing mutations.

22 Mar 2009

New tumor markers determine therapy intensity

Characteristic changes in the DNA of medulloblastoma, the most frequent malignant brain tumor in childhood, indicate precisely how aggressively the tumor will continue to spread and what the chances of disease relapse are.

17 Mar 2009