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.

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

Study reinforces the importance of healthy living for women

Women who maintain a healthy weight and who have lower perceived stress may be less likely to have chromosome changes associated with aging than obese and stressed women, according to a pilot study that was part of the Sister Study.

16 Mar 2009

Potential pathway for drug intervention

A newly identified molecular pathway that directs stem cells to produce glial cells yields insights into the neurobiology of Down's syndrome and a number of central nervous system disorders characterized by too many glial cells, according to a recent study by researchers at the Salk Institute for Biological Studies.

15 Mar 2009

Researchers look at genetic dynamics of inbreeding depression

Researchers have taken a first look at the broad genetic changes that accompany reproductive declines in inbred populations.

12 Mar 2009

Smokers' chronic obstructive pulmonary disease risk is genetic

It's well known that puffing on cigarettes can eventually leave you out of puff.

11 Mar 2009

Measuring the strength needed to move chromosomes

It's about as long as the width of a human hair and only half that length across. So it's tiny - measured in millionths of a meter - and extremely tricky to manipulate. But the meiotic spindle plays so irresistibly important a role in separating our chromosomes during cell division that scientists are compelled to try to study it.

11 Mar 2009

Molecule tracking reveals mechanism of chromosome separation in dividing cells

University of Washington (UW) researchers are helping to write the operating manual for the nano-scale machine that separates chromosomes before cell division.

8 Mar 2009

Genes more important in cleft lip and palate than previously thought

Comparing 500,000 snippets of human DNA put scientists from the University of Bonn on the right track.

8 Mar 2009

Blood test predicts chance of frontal lobe dementia

Frontal lobe dementia (Frontotemporal Dementia, FTD) strikes people at an earlier age. After Alzheimer's disease, FTD is the form of dementia that occurs most frequently in patients younger than 65.

8 Mar 2009

Discovery of new gene associated with Lou Gehrig's disease

A collaborative research effort spanning nearly a decade between researchers at Massachusetts General Hospital (MGH), MIT, the Broad Institute, King's College London (KCL) and other institutions has identified a novel gene for inherited amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease).

5 Mar 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.

3 Mar 2009

Researchers isolate gene mutations in patients with inherited amyotrophic lateral sclerosis

Researchers at the University of Massachusetts Medical School (UMMS) have discovered a new gene whose mutations cause familial amyotrophic lateral sclerosis (ALS), a fatal neurological disorder.

26 Feb 2009

New gene associated with Lou Gehrig's disease

A collaborative research effort spanning nearly a decade between researchers at Massachusetts General Hospital (MGH) and King's College London (KCL) has identified a novel gene for inherited amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease).

26 Feb 2009

A second MND gene mutation in one year signifies rapid research progress

A collaborative research project involving Professor Christopher Shaw of the Institute of Psychiatry, King's College London (KCL), Dr Tom Kwiatkowski at Massachusetts General Hospital (MGH) and Professor Robert H Brown at University of Massachusetts, has revealed that mutations in a gene called FUS (fused in sarcoma) cause familial Motor Neuron Disease (also known as Amyotrophic Lateral Sclerosis).

26 Feb 2009

Significant Rett syndrome discovery

A paper published online today in Nature Neuroscience reveals the presence of methyl CpG binding protein 2 (MeCP2) in glia. MeCP2 is a protein associated with a variety of neurological disorders, including Rett Syndrome, the most physically disabling of the autism spectrum disorders.

23 Feb 2009

Discovery of novel genetic markers linked to increased risk of heart attack

An international team of researchers including scientists of Helmholtz Zentrum München has succeeded in identifying new gene variants associated with an increased risk for myocardial infarction (MI), or heart attack.

17 Feb 2009

2 genes influence social behavior, visual-spatial performance in people with Williams syndrome

Unraveling the genetics of social behavior and cognitive abilities, researchers at the University of Utah and the Salk Institute for Biological Studies have traced the role of two genes,GTF2I and GTF2IRD, in a rare genetic disorder known as Williams Syndrome.

11 Feb 2009