Chromosome 22

Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 49 million DNA base pairs and representing between 1.5 and 2% of the total DNA in cells.
In 1999, researchers working on the Human Genome Project announced they had determined the sequence of base pairs that make up this chromosome. Chromosome 22 was the first human chromosome to be fully sequenced.
Human chromosomes are numbered by their apparent size in the karyotype, with Chromosome 1 being the largest and Chromosome 22 having originally been identified as the smallest. However, genome sequencing has revealed that Chromosome 21 is actually smaller than Chromosome 22.
Genes.
Number of genes.
The following are some of the gene count estimates of human chromosome 22. Because researchers use different approaches to genome annotation their predictions of the number of genes on each chromosome varies (for technical details, see gene prediction). Among various projects, the collaborative consensus coding sequence project (CCDS) takes an extremely conservative strategy. So CCDS's gene number prediction represents a lower bound on the total number of human protein-coding genes.
Gene list.
The following is a partial list of genes on human chromosome 22. For complete list, see the link in the infobox on the right.
Diseases and disorders.
The following diseases are some of those related to genes on chromosome 22:
Chromosomal conditions.
The following conditions are caused by changes in the structure or number of copies of chromosome 22: