Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 21, one copy inherited from each parent, form one of the pairs. Chromosome 21 is the smallest human chromosome, spanning about 47 million base pairs (the building blocks of DNA) and representing approximately 1.5 percent of the total DNA in cells.
In 2000, researchers working on the Human Genome Project announced that they had determined the sequence of base pairs that make up this chromosome. Chromosome 21 was the second human chromosome to be fully sequenced.
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. Chromosome 21 likely contains between 300 and 400 genes.
Genes on chromosome 21 are among the estimated 20,000 to 25,000 total genes in the human genome.
A multistate study led by researchers at the University of Utah has revealed that the risk for childhood cancer is moderately increased among children and young adolescents with certain types of major birth defects.
Scientists at the University of Massachusetts Medical School are the first to establish that a naturally occurring X chromosome "off switch" can be rerouted to neutralize the extra chromosome responsible for trisomy 21, also known as Down syndrome, a genetic disorder characterized by cognitive impairment.
An existing FDA-approved drug improves cognitive function in a mouse model of Down syndrome, according to a new study by researchers at the Stanford University School of Medicine.
Down syndrome, more commonly known as "trisomy 21" is very often accompanied by pathologies found in the general population: Alzheimer's disease, leukemia, or cardiac deficiency.
Sequenom, Inc., a life sciences company providing innovative genetic analysis solutions, today announced that its wholly owned subsidiary, the Sequenom Center for Molecular Medicine, has completed the build-out and validation of an additional laboratory location in Raleigh-Durham, NC, and is now processing patient samples commercially.
Researchers at the Linda Crnic Institute for Down Syndrome and the University of Colorado School of Medicine have found that a single mechanism may underlie the damaging effect of cholesterol on the brain and on blood vessels.
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.
It is well known that people with Down syndrome (DS) suffer from marked muscle weakness. Even the simple tasks of independent living, such as getting out of a chair or climbing a flight of stairs, can become major obstacles. This can reduce the quality of life for those with DS and lead to a loss of independence. Now, a new study sheds light on some of the suspected causes of muscle weakness.
Mice with a condition that serves as a laboratory model for Down syndrome perform better on memory and learning tasks as adults if they were treated before birth with neuroprotective peptides, according to researchers at the National Institutes of Health.
Intellectual disability due to Fragile X and Down syndromes involves similar molecular pathways report researchers in The EMBO Journal. The two disorders share disturbances in the molecular events that regulate the way nerve cells develop dendritic spines, the small extensions found on the surface of nerve cells that are crucial for communication in the brain.
LifeCodexx today announced the successful completion of the clinical validation study of its noninvasive test method for the detection of fetal trisomy 21 from maternal blood using Next Generation sequencing.
Researchers at the University of California, Davis have discovered a key tool that helps sperm and eggs develop exactly 23 chromosomes each. The work, which could lead to insights into fertility, spontaneous miscarriages, cancer and developmental disorders, is published April 13 in the journal Cell.
Down syndrome (DS) is the most common genetic disorder in live born children arising as a consequence of a chromosomal abnormality. It occurs as a result of having three copies of chromosome 21, instead of the usual two. It causes substantial physical and behavioral abnormalities, including life-long cognitive dysfunction that can range from mild to severe but which further deteriorates as individuals with DS age.
Using a noninvasive test on maternal blood that deploys a novel biochemical assay and a new algorithm for analysis, scientists can detect, with a high degree of accuracy, the risk that a fetus has the chromosomal abnormalities that cause Down syndrome and a genetic disorder known as Edwards syndrome.
Research Down Syndrome (RDS), a nonprofit foundation that is among the leading sources for funding of Down syndrome related cognitive research, is entering the second year of its national running program, Race for the Extraordinary, to help increase public awareness and funding for Down syndrome research. The mission of RDS is the development of safe and effective therapies to address the intellectual difficulties associated with Down syndrome.
A healthy genome is characterized by 23 pairs of chromosomes, and even a small change in this structure - such as an extra copy of a single chromosome - can lead to severe physical impairment. So it's no surprise that when it comes to cancer, chromosomal structure is frequently a contributing factor, says Prof. Ron Shamir of the Blavatnik School of Computer Science at Tel Aviv University.
A team of researchers from the University of Utah and the University of Massachusetts has identified the first gene associated with frequent herpes-related cold sores.
Scientists found a deadly parasite with some of its chromosomes in duplicate, others in triplicate, while still others are present four or even five times. Moreover, the copy number varies between individuals. Such a bizarre occurrence has never before been found in nature, in any organism. As a rule, chromosomes should come in couples. The scientists, from the Institute of Tropical Medicine (ITG) and the Wellcome Trust Sanger Institute, made the striking discovery while deciphering the genetic code of a series of Leishmania-parasites.
Investigators have identified a human chromosome containing a specific gene associated with susceptibility to herpes simplex labialis (HSL), the common cold sore.
Pregnant mothers in the U.S. who wish to know whether they're carrying a fetus with Down syndrome now have access to a commercial genetic blood test that has a 99 per cent accuracy rate.
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