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 analyze how Topo II enzyme may affect stability of genomes

While researchers are now familiar with how cancer begins—cells mutate and then multiply wildly out of control—it is still uncertain exactly how that mutation starts in the molecules of the cells.

22 Feb 2016

African Americans with common genetic variants at increased risk for blood clots

New research published online today in Blood, the Journal of the American Society of Hematology (ASH), identifies common genetic variants predominantly found in African Americans that double their risk for blood clots.

18 Feb 2016

Abnormal breakage of chromosomes in white blood cells triggers aggressive form of ALL

A research team led by St. Jude Children's Research Hospital scientists has discovered details of how the abnormal breakage and rearrangement of chromosomes in white blood cells triggers a particularly aggressive form of acute lymphoblastic leukemia (ALL). Such leukemias are cancers of white blood cells, in which genetic mutations trigger overproduction of immature cells, called lymphoblasts.

9 Feb 2016

LouLou Foundation, Penn Med set up Program of Excellence to develop treatments for children with CDKL5

The London-based LouLou Foundation and the Orphan Disease Center of the Perelman School of Medicine at the University of Pennsylvania have established a Program of Excellence to develop effective treatments for children with CDKL5, a rare X-chromosome-linked genetic disorder that causes severe neuro-developmental impairment and early-onset, difficult-to-control seizures.

8 Feb 2016

Researchers identify new targets that may help prevent and cure colon cancer

When the audio on your television set or smart phone is too loud, you simply turn down the volume. What if we could do the same for the signaling in our bodies that essentially causes normal cells to turn cancerous? New discoveries by researchers at the Stephenson Cancer Center at the University of Oklahoma may point to new ways to do just that.

3 Feb 2016

New gene cut-and-paste methods help correct disease-causing mutation in animal model

For the first time, researchers have treated an animal model of a genetic disorder using a viral vector to deliver genome-editing components in which the disease- causing mutation has been corrected.

3 Feb 2016

Two studies shed new light on nature of tandem DNA repeat arrays

A pair of studies by a team of scientists has shed new light on the nature of a particular type of DNA sequences—tandem DNA repeat arrays—that play important roles in transcription control, genome organization, and development.

29 Jan 2016

Scientists find how APOBEC protein becomes dangerous when DNA replication process goes wrong

Cancer is caused by the growth of an abnormal cell which harbours DNA mutations, "copy errors" occurring during the DNA replication process. If these errors do take place quite regularly without having any damaging effect on the organism, some of them affect a specific part of the genome and cause the proliferation of the mutant cell, which then invades the organism.

25 Jan 2016

Study provides evidence for use of inherited genetic markers to improve melanoma prognostication

Melanoma is the most dangerous and lethal form of skin cancer. But just how long will a patient survive following the removal of a melanoma tumor? A more definitive answer to that question could come from new studies at NYU Langone Medical Center and its Laura and Isaac Perlmutter Cancer Center. Researchers there have discovered an inherited genetic marker that might provide clinicians with a personalized tool to gauge an individual's survival and determine which patients require closer monitoring in the years following surgery.

21 Jan 2016

UC Berkeley researchers make major improvement in CRISPR-Cas9 gene editing technology

University of California, Berkeley, researchers have made a major improvement in CRISPR-Cas9 technology that achieves an unprecedented success rate of 60 percent when replacing a short stretch of DNA with another.

21 Jan 2016

Variations in RANBP1 gene may disrupt brain signaling in neuropsychiatric conditions

Scientists have identified a gene that appears to play a significant role in raising a person's risk of having more severe subtypes of autism that co-occur with other genetic diseases, such as the chromosomal disorder 22q11.2 deletion syndrome.

20 Jan 2016

Researchers reveal totally new biological mechanism that underlies cancer

In a landmark study, researchers from the Broad Institute and Massachusetts General Hospital reveal a completely new biological mechanism that underlies cancer. By studying brain tumors that carry mutations in the isocitrate dehydrogenase (IDH) genes, the team uncovered some unusual changes in the instructions for how the genome folds up on itself.

13 Jan 2016

Researchers discover molecular target for DNA repair defects behind Fanconi anemia

Researchers have identified a molecular target and experimental treatment strategy for DNA repair defects behind Fanconi anemia – a complex genetic disorder responsible for birth anomalies, organ damage, anemia and cancer.

12 Jan 2016

U-M research could lead to new ways of fighting X-linked diseases in girls and women

Nearly every girl and woman on Earth carries two X chromosomes in nearly every one of her cells -- but one of them does (mostly) nothing. That's because it's been silenced, keeping most of its DNA locked up and unread like a book in a cage.

11 Jan 2016

DNA damage may lead to mutation and changes in cell

A team of researchers from Colorado State University has been studying DNA damage in living cells to learn more about how genetic abnormalities arise. It has long been known that DNA molecules in every cell get constantly damaged by things from the outside environment, like sunlight, cigarette smoke and radiation. However, more recently researchers have discovered that sources from within the cell itself can sometimes be even more damaging.

7 Jan 2016

Researchers link idiopathic congenital nystagmus to a defect in neurocomputation

Botond Roska and his group at the Friedrich Miescher Institute for Biomedical Research implicate a clearly defined neuron type and its circuit in the retina in the pathophysiology of idiopathic congenital nystagmus.

6 Jan 2016

Researchers successfully use CRISPR to treat adult mouse model of Duchenne muscular dystrophy

Researchers have used CRISPR to treat an adult mouse model of Duchenne muscular dystrophy. This marks the first time that CRISPR has successfully treated a genetic disease inside a fully developed living mammal with a strategy that has the potential to be translated to human therapy.

4 Jan 2016

Researchers identify inherited traits related to sleep, wake and activity cycles

In the first study of its kind, a team of international scientists led by UT Southwestern Medical Center and UCLA researchers have identified a dozen inherited traits related to sleep, wake, and activity cycles that are associated with severe bipolar disorder.

29 Dec 2015

Researchers identify new gene that helps maintain chromosome number in cells

Molecular biologists at UT Southwestern Medical Center have identified a gene called NORAD that helps maintain the proper number of chromosomes in cells, and that when inactivated, causes the number of chromosomes in a cell to become unstable, a key feature of cancer cells.

26 Dec 2015

3D maps of spatial organization may help find genes involved in hereditary diseases

It has now been 15 years since scientists celebrated the completion of the human genome. At that point, scientists had determined the entire sequence of the genetic letters making up our DNA.