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 genetics influences mate choice in humans

New light has been thrown on how humans choose their partners, a scientist will tell the annual conference of the European Society of Human Genetics today (Monday May 25).

24 May 2009

New insights into a new strain of chlamydia

New sequencing and analysis of six strains Chlamydia will result in improved diagnosis of the sexually transmitted infection. This study provides remarkable insights into a new strain of Chlamydia that was identified in Sweden in 2006 after spreading rapidly across the country by evading most established diagnostic tests.

20 May 2009

People with Down syndrome may have more cancer-protective genes

Most cancers are rare in people with Down syndrome, whose overall cancer mortality is below 10 percent of that in the general population. Since they have an extra copy of chromosome 21, it's been proposed that people with Down syndrome may be getting an extra dose of one or more cancer-protective genes.

20 May 2009

Autism discovery may explain why disorder strikes boys four times more than girls

UCLA scientists have discovered a variant of a gene called CACNA1G that may increase a child's risk of developing autism, particularly in boys. The journal Molecular Psychiatry publishes the findings in its May 19 advance online edition.

19 May 2009

Genetic signature may predict patient response to GIST therapy

Researchers at Fox Chase Cancer Center uncovered a genetic pattern that may help predict how gastrointestinal stromal tumor (GIST) patients respond to the targeted therapy imatinib mesylate (Gleevec). Moreover, their findings point to genes that could be suppressed in order to make these tumors respond more readily to imatinib.

15 May 2009

Discovery of eight previously unknown genes that affect blood pressure

Eight previously unknown genes that affect blood pressure were recently identified in a comprehensive international study comprising 34,433 Europeans. The findings of the study, in which Uppsala University researchers participated, are being presented in the Web edition of Nature Genetics.

11 May 2009

New DEAR1 gene predicts local recurrence in early-onset breast cancer

A newly discovered gene known as DEAR1 is mutated in breast cancer and is an independent predictor of local recurrence-free survival in early-onset breast cancer, a research team headed by scientists at The University of Texas M. D. Anderson Cancer Center reports in the journal PLoS Medicine.

5 May 2009

New gene called DEAR1 may be a breast cancer diagnostic marker

In a research article published in this week's PLoS Medicine, Ann Killary (from the University of Texas M. D. Anderson Cancer Center) and colleagues describe a new gene called DEAR1 that is genetically altered by mutation and deletion in breast tumors, and that may provide a new breast cancer prognostic marker.

4 May 2009

CDH10 gene found to play a critical role in prenatal risk of autism

UCLA scientists, in partnership with 30 research institutions across the country, have identified a new gene variant that is highly common in autistic children.

30 Apr 2009

Genes that influence brain cell connections linked to autism

In three studies, including the most comprehensive study of autism genetics to date, investigators funded in part by the National Institutes of Health have identified common and rare genetic factors that affect the risk of autism spectrum disorders.

30 Apr 2009

Gene alterations associated with response to anthracycline therapy for breast cancer

Alterations in the topoisomerase II alpha (TOP2A) gene were associated with better patient outcomes following anthracycline-based therapy compared with non-anthracycline-based regimens, according to a study in the April 28 online issue of the Journal of the National Cancer Institute.

30 Apr 2009

Discovery of gene region that may account for as many as 15 percent of autism cases

A research team has connected more of the intricate pieces of the autism puzzle, with two studies that identify genes with important contributions to the disorder.

30 Apr 2009

Discovery of genetic link for pelvic floor disorders

University of Utah researchers have identified a region of the human genome that may contribute to the development of pelvic floor disorders such as pelvic organ prolapse and stress urinary incontinence, according to a study published this week in the American Journal of Human Genetics .

23 Apr 2009