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.

Preimplantation genetic screening using next generation sequencing: an interview with Dr Luis Alcaraz

PGS, Preimplantation Genetic Screening, is a genetic test that analyses biopsied cells from embryos produced by in vitro fertilization (IVF) techniques. PGS determines whether the embryos are chromosomally normal (euploid) or not (aneuploid), thus giving the chance to transfer chromosomally normal embryos that are more apt to successfully implant and develop into a pregnancy.

24 Aug 2016

Scientists move a step closer to translating BubR1 protein's function into potential cancer therapy

In a paper published recently in the journal eLife, Mayo Clinic scientists take a step toward translating the protein BubR1's function into a potential therapy for cancer.

24 Aug 2016

NIH researchers discover rare, lethal inflammatory disease that affects young children

National Institutes of Health researchers have discovered a rare and sometimes lethal inflammatory disease - otulipenia - that primarily affects young children. They have also identified anti-inflammatory treatments that ease some of the patients' symptoms: fever, skin rashes, diarrhea, joint pain and overall failure to grow or thrive.

23 Aug 2016

Nobel laureate-led study uses new technology to watch interaction between telomerase and telomeres

As the rope of a chromosomes replicates, it frays at the ends. No problem: A chromosome's ends have extra twine so that fraying doesn't reach into the body of the rope where the important information resides.

19 Aug 2016

Study reveals crucial role of TERRA in preservation of telomeres

Despite their especially compact structure that is difficult to access, telomeres transcribe information like the rest of the DNA.

18 Aug 2016

Study offers clues about how genetic mutations can increase risk of psychiatric disorders

Brain scans have revealed how a genetic mutation linked to major psychiatric disorders affects the structure, function and chemistry of the brain.

16 Aug 2016

New study uncovers how chromosomal changes impact tumor formation and growth

As with most cancers, triple-negative breast cancer (TNBC) cells have abnormal amounts of chromosomes or DNA copy number aberrations (CNAs) in their genomes.

16 Aug 2016

New model of Williams syndrome may shed light on neurobiology of the human social brain

In a study spanning molecular genetics, stem cells and the sciences of both brain and behavior, researchers at University of California San Diego, with colleagues at the Salk Institute for Biological Studies and elsewhere, have created a neurodevelopmental model of a rare genetic disorder that may provide new insights into the underlying neurobiology of the human social brain.

11 Aug 2016

New disease gene linked to shortened telomeres appears to raise risk of pulmonary fibrosis-emphysema

Johns Hopkins researchers say they have identified a new disease gene that, when mutated, appears to increase the risk in a small number of people of developing emphysema and a lung-scarring condition known as pulmonary fibrosis.

10 Aug 2016

Geneticists identify enzyme that regulates chromosome segregation during meiosis

GENETICISTS have identified an enzyme which regulates the production of sperm and egg cells in human reproduction.

10 Aug 2016

Researchers discover genetic changes in MSH3 gene in patients with hereditary colon cancer

The formation of large numbers of polyps in the colon has a high probability of developing into colon cancer, if left untreated.

28 Jul 2016

Study reveals insights into survival, surgical interventions for children with trisomy 13 and 18

Among children born with the chromosome disorders trisomy 13 or 18 in Ontario, Canada, early death was the most common outcome, but 10 percent to 13 percent survived for 10 years, according to a study appearing in the July 26 issue of JAMA.

27 Jul 2016

Alterations in genomic region linked to risk of ASD have distinctive effects on cognition, study reports

A new study in Biological Psychiatry reports that variations in 16p11.2, a region of the genome associated with risk of autism spectrum disorder (ASD), have distinct effects on cognition. The findings highlight the diversity of people with ASD.

19 Jul 2016

Scientists explore black box of genome biology

Scientists at Florida State University, Baylor College of Medicine and the Broad Institute of Harvard and MIT have broken ground in a little-understood area of human genetics.

19 Jul 2016

UC Davis scientists show how cells control DNA synthesis in mitochondria

Aging, neurodegenerative disorders and metabolic disease are all linked to mitochondria, structures within our cells that generate chemical energy and maintain their own DNA. In a fundamental discovery with far-reaching implications, scientists at the University of California, Davis, now show how cells control DNA synthesis in mitochondria and couple it to mitochondrial division.

18 Jul 2016

Gender matching may be beneficial to reduce risk of corneal transplant rejection and failure

A study of patients undergoing corneal transplants indicates that subtle differences between men and women may lead to poorer outcomes for a woman who has received a cornea from a male donor.

14 Jul 2016

JAX researchers find precise, reliable way to identify leukemia cells of origin

Every cancer starts with a single cell, and Jackson Laboratory researchers have found a precise and reliable way -- whole-genome profiling of open chromatin -- to identify the kind of cell that leads to a given case of leukemia, a valuable key to cancer prognosis and outcome.

11 Jul 2016

Study finds microRNA let-7 plays key role in restricting neuroblastoma

Great strides have been made in treating neuroblastoma, the most common cancer in infants and toddlers. However, advanced cases are often fatal, and children who survive often face life-long physical and intellectual challenges related to their treatment.

8 Jul 2016

Scientists discover X-chromosome-inherited type of osteogenesis imperfecta

Researchers from the University of Zurich and University Children's Hospital Zurich have discovered the first X-chromosome-inherited type of the congenital disease osteogenesis imperfecta, also known as brittle-bone disease.

6 Jul 2016

Researchers identify astroglia-mediated mechanism for causing FXS symptoms in mice

A study published today in the Journal of Neuroscience led by Yongjie Yang of Tufts University School of Medicine identifies an astroglial trigger mechanism as contributing to symptoms of fragile X syndrome in mice.