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Human GenomeHuman genome is the genome of Homo sapiens. It is made up of 23 chromosome pairs with a total of 3109 base pairs. There are approximately 20,000-25,000 genes in human DNA. The human genome has been mapped by the human genome project. This mapping was finished to 99% on April 14, 2003. Features Human genetic material is made up of two distinct components: the nuclear genome and the mitochondrial genome. The Nuclear Genome The nuclear genome has 24 kinds of chromosomes: numbers 1 through 22 plus the X chromosome and its smaller partner, the Y chromosome. Both men and women inherit 22 chromosomes from each parent, plus an X chromosome which is always inherited from the mother. Women inherit another copy of the X chromosome, and men a copy of the Y chromosome, from the father. The Mitochondrial Genome Both men and women inherit their mitochondrial DNA (mtDNA) from their mother. Internal Features About 97% of the human genome has been designated as "junk" DNA. For example, the Alu sequences are repeated some million or so times, and this one family alone accounts for about 5% of human DNA. Single nucleotide polymorphisms make up 90% of all human genetic variations, and occur every 100 to 300 bases along the human genome. The Genetic Landscape The modern human genome shares more than 97% of its DNA with the rest of the genomes in the Hominid family. See also External Links - National Library of Medicine human genome viewer .
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