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Chromosome 22 is the last of all of them before the sexchromosome, which determines whether the sex is a male or female.

So humans have 46 chromosomes (23 pairs) in each cell. In this writing it is originated in pairs to map out the genes and the expression in genes so far as it is understood by us. Two copies of chromosome 22, one copy inherited from each parent, form one of the pairs. Chromosome 22 is the second smallest human chromosome, spanning more than 51 million DNA building blocks (base pairs) and representing between 1.5 and 2 percent 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 likely contains 500 to 600 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.