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.
Ancient DNA reveals first prehistoric cases of Turner and Jacob's syndromes

Ancient DNA reveals first prehistoric cases of Turner and Jacob's syndromes

Key gene linked to male bias in autism, Tourette's, and ADHD uncovered

Key gene linked to male bias in autism, Tourette's, and ADHD uncovered

New study provides insights about mosaic chromosomal alterations in diverse populations

New study provides insights about mosaic chromosomal alterations in diverse populations

Copy number profiling provides insight as to why prostate cancer may become lethal

Copy number profiling provides insight as to why prostate cancer may become lethal

Simple blood tests for telomeric protein could provide a valuable screen for certain cancers

Simple blood tests for telomeric protein could provide a valuable screen for certain cancers

Pathological significance of CEACAMS 1, 5, and 6 in cancer biology, immunology and inflammatory disease

Pathological significance of CEACAMS 1, 5, and 6 in cancer biology, immunology and inflammatory disease

3D architecture ofAedes aegypti’s chromosomes may offer clues on gene expression, regulation

3D architecture ofAedes aegypti’s chromosomes may offer clues on gene expression, regulation

New blood test can detect prostate cancer with greater accuracy than current methods

New blood test can detect prostate cancer with greater accuracy than current methods

Microscopic technique enables real-time study of RNA G-quadruplexes in living cells

Microscopic technique enables real-time study of RNA G-quadruplexes in living cells

Study identifies the DNA roots of resistance to targeted cancer therapy

Study identifies the DNA roots of resistance to targeted cancer therapy

Persistent tumor mutation burden linked with therapeutic response to immunotherapy

Persistent tumor mutation burden linked with therapeutic response to immunotherapy

Cryo-electron microscopy reveals detailed blueprint of viral genome replication machinery

Cryo-electron microscopy reveals detailed blueprint of viral genome replication machinery

Study provides an estimate of people in the United States with VEXAS syndrome

Study provides an estimate of people in the United States with VEXAS syndrome

Green tea may protect against telomere shortening due to biological aging

Green tea may protect against telomere shortening due to biological aging

Researchers investigate Scandinavian history across 2,000 years

Researchers investigate Scandinavian history across 2,000 years

SynGAP Research Fund awards $180,000 grant to the University of Edinburgh Medical School's Patrick Wild Centre & Centre for Discovery Brain Sciences

SynGAP Research Fund awards $180,000 grant to the University of Edinburgh Medical School's Patrick Wild Centre & Centre for Discovery Brain Sciences

Radiation damage to mature sperm cannot be repaired and is instead passed on to the offspring

Radiation damage to mature sperm cannot be repaired and is instead passed on to the offspring

Non-invasive artificial intelligence approach for IVF embryo selection

Non-invasive artificial intelligence approach for IVF embryo selection

First cell-type specific multiomic study of the HIV brain

First cell-type specific multiomic study of the HIV brain

ACMG's new guideline strongly recommends the use of noninvasive prenatal screening for fetal chromosome abnormalities

ACMG's new guideline strongly recommends the use of noninvasive prenatal screening for fetal chromosome abnormalities