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.
Amyloid plaques — protein clumps that are one of the hallmarks of Alzheimer's disease—occur at roughly the same level in the brains of people with Down syndrome who have Alzheimer's as they do in people with forms of hereditary, early-onset Alzheimer's, according to research funded by the National Institutes of Health.
Individuals with Down syndrome have less-frequent viral infections, but when present, these infections lead to more severe disease.
Gonadotropin-releasing hormone (GnRH) therapy improves cognitive function in Down syndrome (DS) mouse models and male patients with DS, according to a new study.
Children with Down syndrome prefer food with a crispy, oily mouthfeel and don't like brittle or gooey foods. But those preferences can lead to a less nutritious diet, according to Washington State University research published in the Journal of Texture Studies.
Around 80% of people with Down syndrome develop Alzheimer's disease, often when they are between 40 and 50 years old.
New research by a scientist at the Milner Center for Evolution at the University of Bath suggests that "selfish chromosomes" explain why most human embryos die very early on. The study, published in PLoS, Biology, explaining why fish embryos are fine but sadly humans' embryos often don't survive, has implications for the treatment of infertility.
Lamivudine, a commonly-used antiretroviral drug for treating HIV, improves cognition in a mouse model of Down syndrome, according to the findings of a joint new study by researchers at the Centre for Genomic Regulation (CRG) and the IrsiCaixa AIDS Research Institute, a center jointly promoted by the "la Caixa" Foundation and the Department of Health of the Generalitat de Catalunya.
New research shows how genetic variations linked to severe cases of COVID-19 affect our immune cells.
Dutch-French research shows that Optical Genome Mapping (OGM) detects abnormalities in chromosomes and DNA very quickly, effectively and accurately. Sometimes even better than all existing techniques together, as they describe in two proof-of-concept studies published in the American Journal of Human Genetics.
Using ultra-high field magnetic resonance imaging (MRI) to map the brains of people with Down syndrome (DS), researchers from Case Western Reserve University, Cleveland Clinic, University Hospitals and other institutions detected subtle differences in the structure and function of the hippocampus--a region of the brain tied to memory and learning.
A new study led by Belgian and Spanish researchers published in Scientific Reports adds evidence about the potential benefits of green tea extracts in Down syndrome.
A new study by an international team of researchers found that adults with Down syndrome are more likely to die from COVID-19 than the general population, supporting the need to prioritize vaccinating people with the genetic disorder.
A new study describes some potentially important genetic factors in the host that may shape the clinical symptoms and signs of the disease.
Researchers at Karolinska Institutet in Sweden have studied the incidence and regional distribution of Alzheimer's disease biomarkers in the brains of people with Down's syndrome.
The Alzheimer's Biomarkers Consortium - Down Syndrome, a multi-institution research team, co-led by members from the University of California, Irvine, has been awarded an unprecedented five-year, $109 million grant by the National Institutes of Health, to expand research on the biomarkers of Alzheimer's disease in adults with Down syndrome.
Results of a genome-wide association study on 2,244 critically-ill patients due to coronavirus disease (COVID-19) from 208 intensive care units across the United Kingdom revealed significant host-specific genetic determinants that can predispose people to the severe form of the disease. The report is currently available on the medRxiv preprint server.
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.