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.

Study links genetic variation, wheezing illness to childhood asthma risk

About 90 percent of children with two copies of a common genetic variation and who wheezed when they caught a cold early in life went on to develop asthma by age 6, according to a study to be published March 28 by the New England Journal of Medicine.

28 Mar 2013

Study examines specific form of autism caused by duplication on chromosome 15

Identifying and understanding the combination of factors that leads to autism is an ongoing scientific challenge. This developmental disorder appears in the first three years of life, and affects the brain's normal development of social and communication skills.

27 Mar 2013

Study reveals role of SNX27 protein in brain function

What is it about the extra chromosome inherited in Down syndrome-chromosome 21-that alters brain and body development? Researchers at Sanford-Burnham Medical Research Institute have new evidence that points to a protein called sorting nexin 27, or SNX27.

25 Mar 2013

Researchers complete phase II clinical trial of dasatinib for patients with higher-risk MDS

Researchers at Moffitt Cancer Center have completed a phase II clinical trial to determine the safety and efficacy of dasatinib for patients with higher-risk myelodysplastic syndromes, chronic myelomonocytic leukemia, or acute myeloid leukemia resulting from MDS and have failed treatment with azanucleosides.

21 Mar 2013

Study explores new mechanism that may contribute to development of cancers

A study published today in the journal Nature Genetics explores a new mechanism that may contribute to the development of several tumours, including Chronic Lymphocytic Leukaemia, a type of cancer that affects more than a thousand new patients in Spain each year.

20 Mar 2013

CHOP expert to receive Pediatric Oncology Award from ASCO

The American Society of Clinical Oncology today announced it will confer one of its highest awards on pediatric oncologist Garrett M. Brodeur, M.D., of the Cancer Center at The Children's Hospital of Philadelphia.

16 Mar 2013

Mini-chromosome maintenance protein can change DNA topology: Study

A team of USC scientists has identified a protein that can change DNA topology, making DNA twist up into a so-called "supercoil."

12 Mar 2013

Insight into how protein synthesis and degradation help regulate delicate ballet of cell division

Biochemists at the University of Massachusetts Amherst including assistant professor Peter Chien recently gained new insight into how protein synthesis and degradation help to regulate the delicate ballet of cell division. In particular, they reveal how two proteins shelter each other in "mutually assured cleanup" to insure that division goes smoothly and safely.

5 Mar 2013

Structural connectome maps reveal new details about agenesis of the corpus callosum

Combining hospital MRIs with the mathematical tool known as network analysis, a group of researchers at UC San Francisco and UC Berkeley have mapped the three-dimensional global connections within the brains of seven adults who have genetic malformations that leave them without the corpus callosum, which connects the left and right sides of the brain.

1 Mar 2013

Gene mutation findings classify renal cell carcinoma

Researchers have identified mutation-defined subtypes of clear cell renal cell carcinoma that have distinct clinical outcomes.

20 Feb 2013

Healthy adults with shorter telomere length more likely to develop upper respiratory infection

Among healthy adults who were administered a cold virus, those with shorter telomere length (a structure at the end of a chromosome) in certain cells were more likely to develop experimentally-induced upper respiratory infection than participants with longer telomeres, according to results of preliminary research published in the February 20 issue of JAMA.

20 Feb 2013

Article details mechanism by which long non-coding RNA-activators promote gene expression

Long segments of RNA- encoded in our DNA but not translated into protein-are key to physically manipulating DNA in order to activate certain genes, say researchers at The Wistar Institute. These non-coding RNA-activators (ncRNA-a) have a crucial role in turning genes on and off during early embryonic development, researchers say, and have also been connected with diseases, including some cancers, in adults.

18 Feb 2013

Scientists discover new subgroups of GC patients with different disease's characteristics

A collaboration between Portuguese and Italian scientists has discovered new subgroups of stomach cancer patients with different disease's characteristics, an information that is hoped will help improving the clinical management of a disease that still kills a dismaying 3 out of 4 patients.

18 Feb 2013

Study identifies regions of genes linked to Beh-et's disease

Researchers don't know the exact cause of Beh-et's disease, a chronic condition that leads to oral and genital sores and serious complications such as blindness, but new research brings better understanding to what makes some people more susceptible to being affected.

16 Feb 2013

University of Utah geneticists engineer mice that develop clear cell sarcoma

Geneticists led by University of Utah Nobel Prize Laureate Mario R. Capecchi, Ph.D., have engineered mice that develop clear cell sarcoma (CCS), a significant step in better understanding how this rare and deadly soft tissue cancer arises. The mouse model also can potentially speed the development of drugs to target genes that must be activated for the cancer to form.

13 Feb 2013

Key details of how TRF2 protein performs crucial chromosome-protecting function

We take it for granted that our chromosomes won't stick together, yet this kind of cellular disaster would happen constantly were it not for a protein called TRF2. Now, scientists at The Scripps Research Institute (TSRI) have discovered key details of how TRF2 performs this crucial chromosome-protecting function.

7 Feb 2013

Migraine, epilepsy and genetics: an interview with Dr. Melodie Winawer

This work is the product of an extraordinary consortium called the Epilepsy Phenome/Genome project (EPGP). It is a consortium of 27 centres in the U.S. and internationally with several hundred physicians and staff who have worked together to enrol more than 4000 patients with epilepsy and their family members.

7 Feb 2013

Researchers identify mechanism by which vancomycin resistance spreads between bacteria

Worldwide, many strains of the bacterium Staphyloccocus aureus, commonly known as staph infections, are already resistant to all antibiotics except vancomycin. But as bacteria are becoming resistant to this once powerful antidote, S. aureus has moved one step closer to becoming an unstoppable killer.

31 Jan 2013

Bipolar pedigree endophenotypes found

Researchers have found cognitive endophenotypes in a single extended family showing linkage of bipolar disorder to a risk locus on chromosome 4.

30 Jan 2013

Novartis receives FDA approval for Ph+ acute lymphoblastic leukemia

The U.S. Food and Drug Administration today approved a new use of Gleevec (imatinib) to treat children newly diagnosed with Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL).

27 Jan 2013