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.
Russian scientists uncover previously unknown effect of leukemia drug

Russian scientists uncover previously unknown effect of leukemia drug

KU Leuven researchers unravel how cell division timer works

KU Leuven researchers unravel how cell division timer works

Research casts light on how chromosomes 'cheat' for chance to get into a sex cell

Research casts light on how chromosomes 'cheat' for chance to get into a sex cell

Scientists identify treatments that may restore brain function to autism patients

Scientists identify treatments that may restore brain function to autism patients

Our chromosomes also wrinkle with age, research shows

Our chromosomes also wrinkle with age, research shows

New gene drive approach helps pinpoint combination therapies against fungal pathogens

New gene drive approach helps pinpoint combination therapies against fungal pathogens

New analysis method allows to efficiently search for gene transfers onto Y chromosome

New analysis method allows to efficiently search for gene transfers onto Y chromosome

Study discovers new genetic risk loci linked to children's food allergies

Study discovers new genetic risk loci linked to children's food allergies

Genomic roots of ovarian tumors may arise in fallopian tubes, study suggests

Genomic roots of ovarian tumors may arise in fallopian tubes, study suggests

Chromosomes may be entangled, research finds

Chromosomes may be entangled, research finds

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