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.
Pediatric researchers have developed the first set of growth charts for U.S. children with Down syndrome since 1988. These new charts provide an important tool for pediatricians to evaluate growth milestones for children and adolescents with this condition. With these new charts, pediatricians will be able to compare each patient's growth patterns with peers of the same age and sex who have Down syndrome.
For people with Down syndrome, news from Elixirgen, LLC may brighten their day. The biotechnology company, located in the Science + Technology Park at Johns Hopkins, has outlined one of the best potential therapies yet for people with Down syndrome and other chromosome disorders in a paper entitled, "Correction of Down syndrome and Edwards syndrome aneuploidies in human cell cultures," published in the journal DNA Research.
The term intellectual disability covers a large number of clinical entities, some with known cause and others of uncertain origin. For example Down syndrome is due to an extra copy of chromosome 21 and Rett syndrome is in part caused by a mutation in the control switch gene called MeCP2.
Researchers at the University of Kentucky's Sanders-Brown Center on Aging have completed a study that revealed differences in the way brain inflammation -- considered a key component of AD-- is expressed in different subsets of patients, in particular people with Down syndrome (DS) and AD.
Prenatal blood screening for extra or missing chromosomes in the fetus might give false-positive results if the mother's genome contains more than the usual number of certain DNA segments.
A new prenatal test for Down’s Syndrome may be more effective at diagnosing the condition than the standard screening that is currently used, suggests a study published in the New England Journal of Medicine.
Scientists at The Scripps Research Institute have found diverse genomic changes in single neurons from the brains of Alzheimer's patients, pointing to an unexpected factor that may underpin the most common form of the disease.
Down syndrome is the most common chromosomal abnormality in humans, involving a third copy of all or part of chromosome 21. In addition to intellectual disability, individuals with Down syndrome have a high risk of congenital heart defects. However, not all people with Down syndrome have them – about half have structurally normal hearts.
Scientists armed with a supercomputer and a vast trove of newly collected data on the body's most potent "tumor suppressor" gene have created the best map yet of how the gene works, an accomplishment that could lead to new techniques for fighting cancers, which are adept at disabling the gene in order to thrive.
Although doctors have long known that people with Down syndrome have a heightened risk of developing acute lymphoblastic leukemia (ALL) during childhood, they haven't been able to explain why. Now, a team of Dana-Farber Cancer Institute investigators has uncovered a connection between the two conditions.
Occurring in about one per eight hundred births, Down syndrome - or trisomy 21 - is the most frequent genetic cause of intellectual disability. It results from a chromosomal abnormality where cells of affected individuals contain a third copy of chromosome 21 (1% of the human genome).
Researchers have found that people born with a rare abnormality of their chromosomes have a 2,700-fold increased risk of a rare childhood leukaemia. In this abnormality, two specific chromosomes are fused together but become prone to catastrophic shattering.
Scientists at A*STAR's Institute of Molecular and Cell Biology (IMCB) have identified the precise role of the protein, SNX27, in the pathway leading to memory and learning impairment.
The Scientific Advisory Board of the Jerome Lejeune Foundation USA has recommended 4 U.S. researchers to receive grants from the Foundation for its second funding cycle of 2013.
Donna Wilcock of the University of Kentucky Sanders-Brown Center on Aging is the lead investigator on a recently-funded project exploring the links between Alzheimer's disease and Down Syndrome. Elizabeth Head, also of Sanders-Brown Center on Aging, is a co-investigator on the project.
A selective GABA inverse agonist has restored cognitive function in a mouse model of Down's syndrome (DS) and has the potential to benefit humans, French researchers have revealed.
What keeps leukemia cells alive almost forever, able to continue dividing endlessly and aggressively? New research at the Weizmann Institute suggests that, in around a quarter of all leukemias, the cancer cells rely on an internal "balance of terror" to keep going.
Elan Corporation, plc (NYSE: ELN) announced today the first patient dosing in a Phase 2a study of ELND005 in Down syndrome. Study ELND005-DS201 will evaluate the safety and pharmacokinetics of 2 doses of ELND005 and placebo in young adults with Down syndrome without dementia, and will also include select cognitive and behavioural measures.
A recent study by members of the Children's Oncology Group reports results of a large trial showing that children whose leukemia cells have amplification of a portion of chromosome 21 may require more aggressive treatment for Acute Lymphoblastic Leukemia (ALL) than children without this gene amplification.
A pioneering genetic study means that children with a rare subtype of leukaemia have 75% less chance of their leukaemia recurring.
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