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 team of researchers has studied the neural basis of intellectual disability in mice with Down syndrome and has discovered that the neural networks of brain circuits relevant to memory and learning are over-activated and that the connectivity of these circuits is poor.
Amyloid is a key feature of Alzheimer's disease, but the accumulation of these sticky proteins may not be the only risk factor for developing Alzheimer's disease, according to a new study published this week.
Down syndrome, due to an extra chromosome 21, occurs in 250,000 children and adults in the United States, making it the country's most common chromosomal disorder. Inherited heart defects, thyroid cancer, celiac disease and developmental disabilities are common Down syndrome complications.
In a surprising finding using the standard animal model of Down syndrome (DS), scientists were able to correct the learning and memory deficits associated with the condition -- the leading genetic cause of cognitive disability and the most frequently diagnosed chromosomal disorder in the U.S. -- with drugs that target the body's response to cellular stresses.
Professor Juan Lerma's group, from the UMH-CSIC Institute of Neurosciences, in Alicante, has identified the gene called GRIK1, fundamental in the balance between excitation and inhibition in the brain, as one of the causes for people with Down syndrome having spatial orientation problems.
Not so many years ago, people with Down syndrome rarely survived to middle age. Many died young due to heart problems associated with the congenital condition.
Mount Sinai researchers have been awarded a $3.2 million grant from the National Institutes of Health to pursue a deeper understanding of Down syndrome, the most common genetic cause of intellectual and developmental disabilities in children and young adults, affecting more than 200,000 individuals in the United States.
Tarik F. Haydar, PhD, professor of anatomy and neurobiology at Boston University School of Medicine, has been awarded a two-year Exploratory/Developmental Research Grant Award (R21) from the National Institutes of Health.
Targeting a key gene before birth could someday help lead to a treatment for Down syndrome by reversing abnormal embryonic brain development and improving cognitive function after birth, according to a Rutgers-led study.
As part of MIT's continued mission to help build a better world, the Institute announced the creation of the Alana Down Syndrome Center, an innovative new research endeavor, technology development initiative, and fellowship program launched with a $28.6 million gift from Alana Foundation, a nonprofit organization started by Ana Lucia Villela of São Paulo, Brazil.
A study by the Neuropharmacology Laboratory-NeuroPhar of the Department of Experimental and Health Sciences at UPF reveals the involvement of the endocannabinoid system in cognitive disorders in mouse models of Down syndrome.
Dementia is common to a variety of neurodegenerative diseases such as Alzheimer's disease, Parkinson disease and Down syndrome. This common symptom is one of the major causes of disability and dependency among older people.
A team from the Research Institute of the McGill University Health Centre led by Dr. Donald Vinh, the RI's so-called "Dr. House" because of his research into rare diseases, has discovered a new human disease and the gene responsible for it, paving the way for the proper diagnosis of patients globally and the development of new therapies.
At first glance, Down syndrome and Alzheimer's disease, two severe brain abnormalities, may seem to have little in common. Down syndrome is a hereditary disease, the source of which has long been recognized--a triplication of chromosome 21.
Down's syndrome - also known as trisomy 21 - is a genetic disorder caused by an additional third chromosome 21. Although this genetic abnormality is found in one out of 700 births, only 20% of foetuses with trisomy 21 reach full term.
Some scientists call it the "final frontier" of our DNA -- even though it lies at the center of every X-shaped chromosome in nearly every one of our cells.
Research by Jue Wang, MD, at the University of Arizona Cancer Center at Dignity Health St. Joseph's Hospital and Medical Center on "Delay in Diagnosis of Testicular Cancer in a Patient with Down Syndrome" was published in the October issue of Journal of Cancer and Therapeutic Science.
Most living cells have a defined number of chromosomes: Human cells, for example, have 23 pairs. As cells divide, they can make errors that lead to a gain or loss of chromosomes, which is usually very harmful.
A phase 2 clinical trial in young adults with Down syndrome of a drug being investigated for the treatment of Alzheimer's disease supports further investigation of its potential.
Findings from new research led by the Monash Biomedicine Discovery Institute and University College London may finally resolve, and potentially provide answers, as to why older women have higher incidences of miscarriage and have babies with chromosomal abnormalities.