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.
Researchers describe novel mechanism that links epigenetic change to translational control

Researchers describe novel mechanism that links epigenetic change to translational control

Study links spinal muscular atrophy disease expression with haplotypes

Study links spinal muscular atrophy disease expression with haplotypes

Short telomeres could be independent risk factor for age-related functional decline

Short telomeres could be independent risk factor for age-related functional decline

Breakthrough study sheds light on mechanism underlying Warsaw Breakage Syndrome

Breakthrough study sheds light on mechanism underlying Warsaw Breakage Syndrome

Novel method using big data tools shows promising routes for research

Novel method using big data tools shows promising routes for research

Subcutaneous injection of new protein helps treat hemophilia more effectively

Subcutaneous injection of new protein helps treat hemophilia more effectively

Muscle dystrophy treatment in dogs with Crispr gene editing

Muscle dystrophy treatment in dogs with Crispr gene editing

FDA accepts Bristol-Myers Squibb’s application for Sprycel for treating pediatric leukemia

FDA accepts Bristol-Myers Squibb’s application for Sprycel for treating pediatric leukemia

Scientists explore DNA replication errors that can lead to cancer

Scientists explore DNA replication errors that can lead to cancer

Researchers develop 3D map of the human genome

Researchers develop 3D map of the human genome

Study reveals how gene variant affects chronic pain outcomes after trauma

Study reveals how gene variant affects chronic pain outcomes after trauma

Researchers uncover how RNA regulates genes during critical stage in embryonic brain development

Researchers uncover how RNA regulates genes during critical stage in embryonic brain development

Study shows that rogue proteins may underlie some ALS and frontotemporal dementia cases

Study shows that rogue proteins may underlie some ALS and frontotemporal dementia cases

Scientists identify pathways that reveal insights into mechanism of lung cancer etiology

Scientists identify pathways that reveal insights into mechanism of lung cancer etiology

Scientists uncover key control mechanism of DNA replication

Scientists uncover key control mechanism of DNA replication

Brown University researchers reveal key physical properties of 'giant' cancer cells

Brown University researchers reveal key physical properties of 'giant' cancer cells

FDA approves first oral medication for treatment of adults with Fabry disease

FDA approves first oral medication for treatment of adults with Fabry disease

Koala virus could provide clues to accumulated 'junk' DNA in the human genome

Koala virus could provide clues to accumulated 'junk' DNA in the human genome

Study finds false negatives in common tests used to determine ROS1 status in lung cancer

Study finds false negatives in common tests used to determine ROS1 status in lung cancer

Genetic testing before embryo transfer makes no difference to live birth rates

Genetic testing before embryo transfer makes no difference to live birth rates