Chromosome 21 (human)

Chromosome 21 (human)

Pair of human chromosome 21 (after G-banding).
One is from mother, one is from father.

Chromosome 21 pair in human male karyogram.
Features
Length (bp) 48,129,895
Number of genes 477 (NCBI)
635 (EBI)
Type Autosome
Centromere position Acrocentric[1]
Identifiers
RefSeq NC_000021
GenBank CM000683
Map of Chromosome 21
Ideogram of human chromosome 21. Mbp means mega base pair. See locus for other notation.

Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is the smallest human chromosome, with 48 million nucleotides (the building material of DNA) representing about 1.5 percent of the total DNA in cells. The trisomy of the 21st chromosome causes Down syndrome. People without Down's syndrome have two copies of this chromosome.

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, after chromosome 22.

Identifying genes on each chromosome is an active area of genetic research. However, because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Depending on the genome annotation used, chromosome 21 contains 477 or 635 genes.[2][3]

Genes

The following are some of the genes located on chromosome 21:

Diseases and disorders

The following diseases are some of those related to genes on chromosome 21:

Chromosomal conditions

Translocation Down's syndrome affecting Chromosome 21

The following conditions are caused by changes in the structure or number of copies of chromosome 21:

References

  1. "Table 2.3: Human chromosome groups". Human Molecular Genetics (2nd ed.). Garland Science. 1999.
  2. "Map Viewer". National Center for Biotechnology Information. Retrieved November 17, 2013.
  3. "Vega Genome Browser 54: Homo sapiens - Chromosome summary - Chromosome 21: 1-48,119,895". Wellcome Trust Sanger Institute. Retrieved November 17, 2013.
  4. 1 2 3 Sleegers K, Brouwers N, Gijselinck I, Theuns J, Goossens D, Wauters J, Del-Favero J, Cruts M, van Duijn CM, Van Broeckhoven C (2006). "APP duplication is sufficient to cause early onset Alzheimer's dementia with cerebral amyloid angiopathy". Brain. 129 (Pt 11): 2977–83. doi:10.1093/brain/awl203. PMID 16921174.
  5. Gardiner K, Davisson M (2000). "The sequence of human chromosome 21 and implications for research into Down syndrome". Genome Biol. 1 (2): REVIEWS0002. doi:10.1186/gb-2000-1-2-reviews0002. PMC 138845Freely accessible. PMID 11178230.
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