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 solve mystery of final blood group system

Researchers solve mystery of final blood group system

Researchers discover potential target genes to halt thyroid cancer progression

Researchers discover potential target genes to halt thyroid cancer progression

Modular gene enhancers may be suitable target in treatment of blood cancer

Modular gene enhancers may be suitable target in treatment of blood cancer

Three-dimensional organization of genome plays key role in gene expression, cell fate

Three-dimensional organization of genome plays key role in gene expression, cell fate

WPI professor receives Smith Family Foundation grant to explore biology of cancer cells

WPI professor receives Smith Family Foundation grant to explore biology of cancer cells

MGH study points toward potential strategy for treating X-linked disorders

MGH study points toward potential strategy for treating X-linked disorders

Study illustrates the role of alcohol in causing damage to DNA and increased cancer risk

Study illustrates the role of alcohol in causing damage to DNA and increased cancer risk

Scientists show how alcohol exposure leads to permanent genetic damage

Scientists show how alcohol exposure leads to permanent genetic damage

Study uncovers genomic targets in refractory neuroblastoma

Study uncovers genomic targets in refractory neuroblastoma

Novartis announces FDA approval of its first and only CML therapy with TFR data in product label

Novartis announces FDA approval of its first and only CML therapy with TFR data in product label

Having older brothers may increase the likelihood of being gay

Having older brothers may increase the likelihood of being gay

Simple molecular test may help predict presence of high-grade pancreatic cancers

Simple molecular test may help predict presence of high-grade pancreatic cancers

SLU scientists provide promising approach in designing new drugs for DMD

SLU scientists provide promising approach in designing new drugs for DMD

Study shows how interplay between two key enzymes promotes brain tumor growth

Study shows how interplay between two key enzymes promotes brain tumor growth

Research shows how cells rebuild nucleus, organize genome after division

Research shows how cells rebuild nucleus, organize genome after division

Leishmania genome study reveals the parasites adaptation to the environment

Leishmania genome study reveals the parasites adaptation to the environment

Leishmania adaptation to environmental changes results from frequent chromosomal amplifications

Leishmania adaptation to environmental changes results from frequent chromosomal amplifications

OBD presents results of immunotherapy studies at FNIH Biomarker Consortium Cancer Steering Committee’s annual meeting

OBD presents results of immunotherapy studies at FNIH Biomarker Consortium Cancer Steering Committee’s annual meeting

New technique may reveal clues about role of centromeres in Down syndrome, other birth defects

New technique may reveal clues about role of centromeres in Down syndrome, other birth defects

Aging tests disagree with one another

Aging tests disagree with one another