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.
Non-invasive genetic test for fetal DNA sequencing developed

Non-invasive genetic test for fetal DNA sequencing developed

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

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

Exploring developmental pathways and disease interactions in nervous and stomatognathic systems

Exploring developmental pathways and disease interactions in nervous and stomatognathic systems

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

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

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

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

Study reveals immune dysregulation in Down syndrome and potential therapeutic strategy

Study reveals immune dysregulation in Down syndrome and potential therapeutic strategy

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

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

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

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

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

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

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

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

Scientists identify the cause of leukemia in people with trisomy 21

Scientists identify the cause of leukemia in people with trisomy 21

Scientists identify mechanisms underlying autoimmunity in Down syndrome

Scientists identify mechanisms underlying autoimmunity in Down syndrome

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

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

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

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

GnRH therapy could improve cognitive deficits in men with Down syndrome

GnRH therapy could improve cognitive deficits in men with Down syndrome

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

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

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

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

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

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

Antiretroviral drug used to treat HIV ameliorates cognitive deficits in mouse model of Down syndrome

Antiretroviral drug used to treat HIV ameliorates cognitive deficits in mouse model of Down syndrome

Study explores connections between COVID-19 severity and gene expression in immune cells

Study explores connections between COVID-19 severity and gene expression in immune cells