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.

First evidence that complex genetic interactions account for autism risk

Using a novel analysis of the interactions among related genes, Duke University Medical Center researchers have uncovered some of the first evidence that complex genetic interactions account for autism risk. The Duke team found that the brain mechanism that normally stops or slows nerve impulses contributes to the disease.

3 Aug 2005

Customized gene chip offers clues to prognosis in cases of neuroblastoma

Rather than covering the entire genome, the microarray focuses on suspect regions of chromosomes for signs of deleted genetic material known to play a role in the cancer.

2 Aug 2005

Customized gene chip will offer clues to prognosis in cases of neuroblastoma

Genetics researchers have developed a customized gene chip to rapidly scan tumor samples for specific DNA changes that offer clues to prognosis in cases of neuroblastoma, a common form of children's cancer.

2 Aug 2005

Exposure to second-hand smoke during pregnancy can be just as detrimental to a developing fetus as primary exposure through maternal smoking

In a study published in the online journal BMC Pediatrics, Stephen G. Grant, Ph.D., associate professor of environmental and occupational health, reports that both active maternal smoking and secondary maternal exposure result in similarly increased rates of genetic mutation that are basically indistinguishable.

26 Jul 2005

Multi-species genome comparison sheds new light on evolutionary processes

An international team that includes researchers from the National Human Genome Research Institute (NHGRI) has discovered that mammalian chromosomes have evolved by breaking at specific sites rather than randomly as long thought - and that many of the breakage hotspots are also involved in human cancer.

25 Jul 2005

Scientists have identified the first genetic mutations that cause the aorta to widen, tear and rupture

Finding biological markers that flag aneurysm, a bulging of the aorta that leads to dissection, a lengthwise separation of tissues in the artery wall, is critically important for early diagnosis.

25 Jul 2005

Gene that regulates normal embryonic development is found at high levels in virtually all forms of breast cancer

A gene that appears to help regulate normal embryonic development is found at high levels in virtually all forms of breast cancer, according to a new study led by Laszlo Radvanyi, Ph.D., associate professor of breast and melanoma medical oncology at The University of Texas M. D. Anderson Cancer Center.

25 Jul 2005

New insight into age-related macular degeneration

Age-related macular degeneration is the leading cause of blindness in older adults, yet researchers are still in the dark about many of the factors that cause this incurable disease.

25 Jul 2005

Multiple rare mutations within a single gene may increase risk for autism

While debate still rages over the 'cause' of autism, mounting evidence suggests that genetic factors play a major role in the disease.

25 Jul 2005

Hidden secrets on the nature and timing of genome evolution in mammals revealed

Breakages in chromosomes in mammalian evolution have occurred at preferred rather than random sites as long thought, and many of the sites are involved in human cancers, an international team of 25 scientists has discovered.

21 Jul 2005

Two regions of the human genome that appear to explain variation in IQ

It may be that IQ tests are not the only way to measure human intelligence. Scientists at The Queensland Institute of Medical Science (QIMR) have identified two regions of the human genome that appear to explain variation in IQ. Their work was published this week in the American Journal of Human Genetics and has drawn world-wide interest.

19 Jul 2005

Extraordinary number of genes are required for prenatal mammalian development

A team of scientists led by Cornell University's Dr. John Schimenti reports today that an extraordinary number of genes are required for prenatal mammalian development. The researchers estimate that up to 19% of all genes are vital for embryogenesis in mice.

17 Jul 2005

Chromos Molecular Systems issued four key patents

Chromos Molecular Systems has announced that it has further expanded the patent portfolio surrounding both its ACE System and REM Technology with the issuance of four key additional patents.

15 Jul 2005

Researchers find genetically controlled brain mechanism responsible for social behavior in humans

Researchers at the National Institute of Mental Health (NIMH) have discovered a genetically controlled brain mechanism responsible for social behavior in humans--one of the most important but least understood aspects of human nature.

13 Jul 2005

Researchers have pinpointed specific gene and protein over-production in metastatic melanoma

Gene amplification is a process that often happens in cancer cells when the normal DNA replication process is altered, causing many copies of the gene to be produced instead of a single copy of a region of a chromosome.

12 Jul 2005

Researchers discover genetically controlled brain mechanism responsible for social behavior in humans

Researchers at the National Institute of Mental Health (NIMH) have discovered a genetically controlled brain mechanism responsible for social behavior in humans - one of the most important but least understood aspects of human nature. The findings are reported in Nature Neuroscience.

11 Jul 2005

Changes to prenatal genetic testing could mean more babies born with abnornalities

A study in the UK suggests that a proposed change to the type of prenatal genetic testing offered to couples in the UK, could possibly result in certain chromosome abnormalities being missed.

4 Jul 2005

Birth abnormality rates could increase if proposed changes to prenatal testing go ahead

A proposed change to the type of prenatal genetic testing offered to couples in the UK could result in certain chromosome abnormalities being missed, suggests a study published online today (Thursday June 30, 2005) by The Lancet.

1 Jul 2005

New initiative to provide $600k to fund new research into Down Syndrome

Today the University of Colorado and The Anna and John J. Sie Foundation of Denver announced The Sie Family Down Syndrome Break-Through Research Initiative. The initiative will provide $600,000 in grant funds to stimulate new scientific research on Down syndrome with the aim of enhancing cognitive ability. These are the first such grants provided to CU for a specific chromosomal condition and the first nationwide specifically for Down syndrome.

1 Jul 2005

Exercise helps find genetic regions linked to prediabetes

People's bodies respond to exercise in different ways, and their genetic makeup is partly responsible.

28 Jun 2005

Chromosome X News and Research

Further Reading

First evidence that complex genetic interactions account for autism risk

Customized gene chip offers clues to prognosis in cases of neuroblastoma

Customized gene chip will offer clues to prognosis in cases of neuroblastoma

Exposure to second-hand smoke during pregnancy can be just as detrimental to a developing fetus as primary exposure through maternal smoking

Multi-species genome comparison sheds new light on evolutionary processes

Scientists have identified the first genetic mutations that cause the aorta to widen, tear and rupture

Gene that regulates normal embryonic development is found at high levels in virtually all forms of breast cancer

New insight into age-related macular degeneration

Multiple rare mutations within a single gene may increase risk for autism

Hidden secrets on the nature and timing of genome evolution in mammals revealed

Two regions of the human genome that appear to explain variation in IQ

Extraordinary number of genes are required for prenatal mammalian development

Chromos Molecular Systems issued four key patents

Researchers find genetically controlled brain mechanism responsible for social behavior in humans

Researchers have pinpointed specific gene and protein over-production in metastatic melanoma

Researchers discover genetically controlled brain mechanism responsible for social behavior in humans

Changes to prenatal genetic testing could mean more babies born with abnornalities

Birth abnormality rates could increase if proposed changes to prenatal testing go ahead

New initiative to provide $600k to fund new research into Down Syndrome

Exercise helps find genetic regions linked to prediabetes

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