Chromosome 21 News and Research

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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.

Historic DNA analysis identifies Down and Edwards syndromes in ancient humans

By analyzing ancient DNA, an international team of researchers have uncovered cases of chromosomal disorders, including what could be the first case of Edwards syndrome ever identified from prehistoric remains.

20 Feb 2024

Researchers uncover a gene that causes heart defects in Down syndrome

Researchers at the Francis Crick Institute and UCL have identified a gene that causes heart defects in Down syndrome, a condition that results from an additional copy of chromosome 21.

24 Jan 2024

Non-invasive genetic test for fetal DNA sequencing developed

A team of investigators from Massachusetts General Hospital (MGH), Brigham and Women's Hospital (BWH), and the Broad Institute of MIT and Harvard have developed a non-invasive genetic test that can screen the blood of pregnant individuals to survey all genes for fetal DNA sequence variants.

22 Nov 2023

Texas A&M researchers win NIH grant to study metabolism in people with Down syndrome

A team of researchers at the Texas A&M University School of Veterinary Medicine & Biomedical Sciences (VMBS) has received a grant from the National Institutes of Health (NIH) to research metabolism in people with Down syndrome.

17 Oct 2023

Exploring developmental pathways and disease interactions in nervous and stomatognathic systems

Scientists discuss the intricate relationship between the nervous and stomatognathic systems.

21 Aug 2023

$11 million NIH grant focuses on cognitive function in Down syndrome-associated Alzheimer’s

Neurologist Beau Ances, MD, PhD, talks with his patient, Adam Kloppenberg, who has Down syndrome, at Washington University School of Medicine in St. Louis. People with Down syndrome are at very high risk of developing Alzheimer's disease. Ances is involved in a project led by Jason Hassenstab, PhD, an associate professor of neurology, to develop tools to measure cognitive function in people with Down syndrome-associated Alzheimer's disease.

3 Aug 2023

Study reveals two key mechanisms underlying high risks from lung infections in Down syndrome

Individuals with Down syndrome, the genetic condition caused by triplication of human chromosome 21, also known as trisomy 21, display a very high risk of hospitalization and mortality after developing lung infections.

2 Aug 2023

Study reveals immune dysregulation in Down syndrome and potential therapeutic strategy

People with Down syndrome, the condition caused by an extra copy of chromosome 21, or trisomy 21, display chronic dysregulation of their immune system, which can contribute to high rates of autoimmune conditions and severe complications from respiratory infections.

17 Jul 2023

Overdosed gene on chromosome 21 accelerates aging in people with Down's syndrome

An overdosed gene on chromosome 21 causes people with Down's Syndrome to age faster than the general population.

12 Jul 2023

Researchers shed light on the genetics behind facial changes in Down syndrome

Researchers at the Francis Crick Institute, King's College London and University College London have shed light on the genetics behind changes in the structure and shape of the face and head in a mouse model of Down Syndrome.

26 Apr 2023

An extra gene causes excessive inhibitory connections in the neocortex of Down syndrome mouse models

An extra copy of a gene that controls synapse formation in the cortex causes excessive inhibitory signaling and may contribute to Down syndrome, according to a new study publishing April 20th in the open access journal PLOS Biology by Bing Ye of the University of Michigan, US, and colleagues.

21 Apr 2023

New genetic animal model may inform potential therapeutic options for Down syndrome

National Institutes of Health researchers compared a new genetic animal model of Down syndrome to the standard model and found the updated version to be more similar to the changes seen in humans.

14 Mar 2023

Scientists identify the cause of leukemia in people with trisomy 21

People with a third copy of chromosome 21, known as trisomy 21, are at high risk of developing Acute Myeloid Leukaemia (AML), an aggressive form of blood cancer.

10 Mar 2023

Scientists identify mechanisms underlying autoimmunity in Down syndrome

Scientists at the Icahn School of Medicine at Mount Sinai in New York have identified which parts of the immune system go awry and contribute to autoimmune diseases in individuals with Down syndrome.

22 Feb 2023

People with Alzheimer’s and Down syndrome may benefit from participating in Alzheimer’s clinical trials

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.

12 Dec 2022

Study reveals why viral infections are less frequent but more severe in individuals with Down syndrome

Individuals with Down syndrome have less-frequent viral infections, but when present, these infections lead to more severe disease.

14 Oct 2022

GnRH therapy could improve cognitive deficits in men with Down syndrome

Gonadotropin-releasing hormone (GnRH) therapy improves cognitive function in Down syndrome (DS) mouse models and male patients with DS, according to a new study.

1 Sep 2022

Study addresses food texture challenges in the life of children with Down syndrome

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.

29 Aug 2022

Simple blood test can accurately detect Alzheimer's disease in people with Down syndrome

Around 80% of people with Down syndrome develop Alzheimer's disease, often when they are between 40 and 50 years old.

24 Aug 2022

"Selfish chromosomes" explain why most human embryos die very early on, study suggests

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.

6 Jul 2022