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.

DNA end caps may lead to cancer treatments

The two ends of human DNA have different structures that are treated differently as a cell divides, UT Southwestern Medical Center researchers have found in a study that could help lead to cancer therapies.

7 Feb 2006

Scientists have determined the detailed structure of an essential piece of the telomerase enzyme

Scientists have determined the detailed structure of an essential piece of the telomerase enzyme, an important contributor to the vast majority of human cancers. Understanding the physical shape of the protein has led to a better understanding of how it acts to immortalize cells - and should help scientists design broadly effective cancer drugs.

5 Feb 2006

Chinese medicine shows promise as treatment for sperm genetic abnormalities

Bioscientists from the University of Kent have called for clinical trials to further investigate how traditional Chinese medicine (TCM) may have a positive effect on sperm genetic abnormalities, and thereby influence the success rate of male infertility treatment.

2 Feb 2006

Counting cells that ensure gene balance

Two are one too many - this is the motto used by cells of a female organism: These contain two X chromosomes, one of which always becomes inactivated.

2 Feb 2006

Identity Swap: Finding the variants that human history has favoured

Sequence differences in less than 0.2% of the 3-billion-base human genome play a vital role in a bewildering variety of human disease. Researchers from the Wellcome Trust Sanger Institute and the Cambridge University’s Cambridge Institute for Medical Research, together with international colleagues report in PLoS Genetics their detailed maps of differences implicated in disease as well as genes that are unchanged in recent human history.

26 Jan 2006

Treatment of down syndrome in mice restores nerve growth in cerebellum

Researchers at Johns Hopkins restored the normal growth of specific nerve cells in the cerebellum of mouse models of Down syndrome (DS) that were stunted by this genetic condition. The cerebellum is the rear, lower part of the brain that controls signals from the muscles to coordinate balance and motor learning.

25 Jan 2006

New method to find new metabolites

Ever since penicillin, a byproduct of a fungal mold, was discovered in 1929, scientists have scrutinized fungi for other breakthrough drugs. As reported Jan. 20 in the Journal of Chemistry and Biology, a team led by a University of Wisconsin-Madison researcher has developed a new method that may speed the ongoing quest for medically useful compounds in fungi.

23 Jan 2006

Protein amplifies DNA injury signals - cues genetic repair mechanism to prevent tumors

A Mayo Clinic-led research collaboration has discovered that the protein MDC1 amplifies weak DNA injury signals so genetic repair can begin.

23 Jan 2006

TCF21 gene shown to be a tumor suppressor

Researchers have identified a new and unusual tumor suppressor gene that may be important in cancers of the lung and head and neck. The study shows that restoring the inactivated gene can slow the growth of tumor cells.

18 Jan 2006

X-linked agammaglobulinemia

Individuals who have a rare genetic immune system disorder that prevents them from making antibodies nevertheless appear to be moderately healthy and lead productive lives, according to results of a study by investigators at St. Jude Children's Research Hospital.

18 Jan 2006

Genetic cause of autism

The researchers at the U School of Medicine made the finding by tracing variations in the DNA of an extended Utah family that has a high occurrence of the disorder and whose members are descended from one couple.

18 Jan 2006

Physiogenomic resources for rat models of heart, lung and blood disorders

Every year, heart disease claims an estimated 7 million lives, according to the World Health Organization. Scientists have struggled to pinpoint the precise genes behind this complex disease. Now, however, they have a new research ally: the designer rat.

16 Jan 2006

Identification of gene in childhood kidney disease

An international research collaboration led by Mayo Clinic has identified a new gene involved in causing the inherited kidney disorder, Meckel-Gruber syndrome (MKS). Children with MKS have central nervous system deformities as well as abnormal cysts in their kidneys, and usually die shortly after birth.

16 Jan 2006

Diabetes gene found in 40% of population

Researchers in Iceland say they have identified a single genetic change which could predispose close to 40 percent of the population to type-2 diabetes.

16 Jan 2006

DinB DNA polymerase is a key player in DNA repair

A quarter century after they discovered it, researchers have identified the job of one of the most common DNA-damage response proteins. The enzyme has puzzled scientists because it is present in nearly every organism, which suggests that it is crucial to life, and yet, in laboratory experiments, its function has remained a mystery.

11 Jan 2006

St. Jude projects 90 percent cure rate for acute lymphoblastic leukemia

The cure rate for the once almost universally fatal childhood cancer acute lymphoblastic leukemia (ALL) could reach 90 percent in the near future, thanks to improvements in diagnosis and treatment over the past four decades, according to investigators at St. Jude Children's Research Hospital.

11 Jan 2006

Gene that increases risk for Alzheimer's disease

An international team of researchers, led by investigators at Washington University School of Medicine in St. Louis, are zeroing in on a gene that increases risk for Alzheimer's disease. They have identified a region of chromosome 10 that appears to be involved in risk for the disease that currently affects an estimated 4.5 million Americans.

10 Jan 2006

DNA polymerase zeta gives cells with damaged DNA a new lease on life

Fortunately, our cells contain many enzymes devoted strictly to detecting and repairing any damage caused by these insults. In fact, failure of these enzymes to make needed repairs to genes can lead to the accumulation of mutations and, eventually, cell death or possibly cancer.

6 Jan 2006

Scientists describe phenomenon in the human genome called transcription-induced chimerism

In the January issue of the journal Genome Research, two teams of scientists describe a widespread phenomenon in the human genome called transcription-induced chimerism (TIC), where two adjacent genes produce a single, fused RNA transcript.

6 Jan 2006

New human embryonic stem cells grown in animal cell-free cultures

Scientists working at the WiCell Research Institute, a private laboratory affiliated with the University of Wisconsin-Madison, have developed a precisely defined stem cell culture system free of animal cells and used it to derived two new human embryonic stem cell.

2 Jan 2006