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.
Research aims to raise awareness of higher rate of testicular cancer in patients with DS

Research aims to raise awareness of higher rate of testicular cancer in patients with DS

New study maps human genome to healthy tissue functions and disease processes

New study maps human genome to healthy tissue functions and disease processes

Researchers use mixed realty viewer to visualize complex biological networks in 3D

Researchers use mixed realty viewer to visualize complex biological networks in 3D

Abnormalities of blood vessels in the brain may play major role in development of schizophrenia

Abnormalities of blood vessels in the brain may play major role in development of schizophrenia

Whitehead Institute scientists identify brain/body connection in genomic region linked to autism

Whitehead Institute scientists identify brain/body connection in genomic region linked to autism

Change in epigenetic gene regulation by imprinting can trigger preeclampsia, study shows

Change in epigenetic gene regulation by imprinting can trigger preeclampsia, study shows

Research findings can lead to new treatment for patients with fatal glandular cancer

Research findings can lead to new treatment for patients with fatal glandular cancer

Pediatric researchers discover gene variants related to aggressive form of neuroblastoma

Pediatric researchers discover gene variants related to aggressive form of neuroblastoma

Researchers discover ‘recycled’ genes in mammalian genome

Researchers discover ‘recycled’ genes in mammalian genome

Lesser-known gene appears to play greater role in Alzheimer's and dementia-related memory decline

Lesser-known gene appears to play greater role in Alzheimer's and dementia-related memory decline

Genome sequence cannot predict radiation resistance, say researchers

Genome sequence cannot predict radiation resistance, say researchers

Researchers develop model to explore hard-to-study mutations in human genome

Researchers develop model to explore hard-to-study mutations in human genome

Penn researchers find abnormally shortened telomeres in young DMD patients’ muscle stem cells

Penn researchers find abnormally shortened telomeres in young DMD patients’ muscle stem cells

Researchers find correlation between shorter telomeres and presence of heart failure

Researchers find correlation between shorter telomeres and presence of heart failure

Split-brain study using fruit fly provides better understanding of autism

Split-brain study using fruit fly provides better understanding of autism

Japanese scientists uncover new genetic marker for schizophrenia

Japanese scientists uncover new genetic marker for schizophrenia

UAB researchers reveal key role for RSF1 protein in silencing genes

UAB researchers reveal key role for RSF1 protein in silencing genes

Human ancestors responsible for transmitting ancient strains of herpesvirus, study finds

Human ancestors responsible for transmitting ancient strains of herpesvirus, study finds

Study sheds new light on gene fusion in bladder and brain cancer

Study sheds new light on gene fusion in bladder and brain cancer

Distinguishing biothreat look-alikes could aid biological surveillance

Distinguishing biothreat look-alikes could aid biological surveillance