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Deoxyribonucleic Acid (DNA)

Formally known as Deoxyribonucleic acid, DNA is the code within biological cells that captures the instructions on how to make different proteins that govern the cells function and form. They consist of long, linear strands of base-pairs consisting of only 4 basic building block molecules. These molecules, in pairs or triples, define larger proteins that, when strung together, create genes and other material that define particular functions. Most of the DNA resides in chromosome strands.

Every human cell has a nucleus with 46 chromosomes. Each chromosome has a type label of either 1 to 22 or X or Y. The numeric labeled chromosomes are called autosomes and the sex or somal chromosomes are X and Y. Every cell has a pair of closely matching, numeric-labeled chromosomes and two somal chromosomes. There are approximately 6.4 biilion base pairs in these 46 chromosomes.

Often overlooked, there is DNA in the cell body, outside the nucleus, as well. These mitochondria structures also contain a ring DNA molecule very similar to the nuclear-residing chromosomes. Mitochondria are important not only for their function in the cell but also in that only the egg copy survives the reproduction process as the sperm copy is destroyed. Thus mitochondria are always passed on only from the mother who produces the egg.

All DNA is built in the well-known "double helix" structure. This is not to be confused with the fact that each nucleus of the cell has a pair of each numbered chromosome. That is to say, for example, there are two similar (but not identical) copies of chromosome 22 in every cell and each chromosome 22 is built as a double-helix structure.

See Also

Autosomes Somal Chromosomes

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