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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 (chromosome 21 being smaller), 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. 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 22 contains about 693 genes. Chromosome 22 was originally identified as the smallest chromosome. After extensive research, however, researchers concluded that chromosome 21 was smaller. The numbering of these chromosomes wasn't rearranged because of chromosome 21 being known by that designation as the chromosome that can lead to Down syndrome. ==Genes== The following are some of the genes located on chromosome 22: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Chromosome 22 (human)」の詳細全文を読む スポンサード リンク
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