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 identify specific target sites for DNA methylases

Researchers identify specific target sites for DNA methylases

Advanced cryo-EM imaging reveals high-resolution structure of viral RNA replication complex

Advanced cryo-EM imaging reveals high-resolution structure of viral RNA replication complex

New test uses a single drop of blood to rapidly detect radiation sickness

New test uses a single drop of blood to rapidly detect radiation sickness

Nix gene can help develop future mosquito control techniques

Nix gene can help develop future mosquito control techniques

Overzealous guardians in the cells could increase cancer risk

Overzealous guardians in the cells could increase cancer risk

Study of lysosomal function during mitosis reveals new biomarker for chromosomal instability

Study of lysosomal function during mitosis reveals new biomarker for chromosomal instability

Risk of severe COVID-19 in ~50 kb genomic segment inherited from Neanderthals

Risk of severe COVID-19 in ~50 kb genomic segment inherited from Neanderthals

New technique to sort out complex interactions unique to prostate cancer cells

New technique to sort out complex interactions unique to prostate cancer cells

Researchers create new tool to identify cancer-causing mutations lurking in 98% of the genome

Researchers create new tool to identify cancer-causing mutations lurking in 98% of the genome

NPHS1 is a disease-susceptibility gene for steroid-sensitive nephrotic syndrome, reveals study

NPHS1 is a disease-susceptibility gene for steroid-sensitive nephrotic syndrome, reveals study

New scanner to detect early signs of bladder cancer could save thousands of lives

New scanner to detect early signs of bladder cancer could save thousands of lives

Glitches in DNA replication have important implications for treating cancer

Glitches in DNA replication have important implications for treating cancer

Scientists discover osmotic stress as stimulator of cellular waste disposal

Scientists discover osmotic stress as stimulator of cellular waste disposal

Researchers identify new protein complex that regulates chromosome separation

Researchers identify new protein complex that regulates chromosome separation

A metabolic enzyme drives B cell lymphomas and could be a potential drug target

A metabolic enzyme drives B cell lymphomas and could be a potential drug target

ACE inhibition in kidney could influence pathogenesis of SARS-CoV-2

ACE inhibition in kidney could influence pathogenesis of SARS-CoV-2

Tomocube holotomography microscopy reveals novel cholesterol membrane transport system in erythrocytes infected with fatal malaria parasite

Tomocube holotomography microscopy reveals novel cholesterol membrane transport system in erythrocytes infected with fatal malaria parasite

Evidence of link between ACE2 genotype and COVID-19 disease severity

Evidence of link between ACE2 genotype and COVID-19 disease severity

Blood types and COVID-19 risk confirmed

Blood types and COVID-19 risk confirmed

Persistent DNA damage in the placenta can affect embryonic growth

Persistent DNA damage in the placenta can affect embryonic growth