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.
MIT biologists identify how the immune system eliminates genetically imbalanced cells

MIT biologists identify how the immune system eliminates genetically imbalanced cells

Phase 2 clinical study examines Alzheimer's disease drug to treat adults with Down syndrome

Phase 2 clinical study examines Alzheimer's disease drug to treat adults with Down syndrome

Research findings may provide answers for infertility in older women

Research findings may provide answers for infertility in older women

Alkaloid in ayahuasca beverage triggers neurogenesis in human neural cells

Alkaloid in ayahuasca beverage triggers neurogenesis in human neural cells

Study shows how oxidative damage may contribute to ‘maternal age effect’

Study shows how oxidative damage may contribute to ‘maternal age effect’

Geneticists identify enzyme that regulates chromosome segregation during meiosis

Geneticists identify enzyme that regulates chromosome segregation during meiosis

Scientists discover new ZBTB7A gene mutation that promotes growth of cancer cells

Scientists discover new ZBTB7A gene mutation that promotes growth of cancer cells

Researchers identify single RCAN1 gene responsible for onset of type 2 diabetes

Researchers identify single RCAN1 gene responsible for onset of type 2 diabetes

Embryos with abnormalities in initial stages of pregnancy may grow into healthy babies

Embryos with abnormalities in initial stages of pregnancy may grow into healthy babies

Researchers develop new technique to create naïve pluripotent stem cells

Researchers develop new technique to create naïve pluripotent stem cells

Report uncovers how Down syndrome hampers nervous system that plays key role in health, longevity

Report uncovers how Down syndrome hampers nervous system that plays key role in health, longevity

Two studies explore potential new blood tests for Alzheimer's disease

Two studies explore potential new blood tests for Alzheimer's disease

Researchers develop new growth charts for U.S. children with Down syndrome

Researchers develop new growth charts for U.S. children with Down syndrome

Gene ZSCAN4 may help treat Down syndrome

Gene ZSCAN4 may help treat Down syndrome

Study finds mechanism that identifies cause of intellectual disabilities in autism, Rett syndrome

Study finds mechanism that identifies cause of intellectual disabilities in autism, Rett syndrome

Study reveals differences in the way brain inflammation is expressed in people with Down syndrome, AD

Study reveals differences in the way brain inflammation is expressed in people with Down syndrome, AD

Researchers analyze false-positive results from new prenatal genetic screens

Researchers analyze false-positive results from new prenatal genetic screens

New prenatal test introduced for detecting Down’s Syndrome

New prenatal test introduced for detecting Down’s Syndrome

Alzheimer's brains commonly have many neurons with more DNA and genomic copies of APP gene

Alzheimer's brains commonly have many neurons with more DNA and genomic copies of APP gene

High risk for congenital heart defects in Down syndrome provides tool to identify changes in genes

High risk for congenital heart defects in Down syndrome provides tool to identify changes in genes