What Do Scientists Look at in DNA Fingerprinting?
The ability to test DNA, the code of life, is one of the most important technological innovations of the 20th century. DNA fingerprinting is a specific kind of test that is used to identify individuals. Like a normal fingerprint, everyone has a specific pattern.
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DNA
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The hereditary material for almost all forms of life is called DNA, or deoxyribonucleic acid, which is mostly contained in the nucleus of the cell. For multicellular organisms, or eukaryotes, DNA is packed within every cell of the body. The one thing that distinguishes one form of life from another is the sequences of DNA.
Base Pairs
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DNA is composed of two double helix strands. Bridging these strands are molecules called base pairs that look like ladder rungs. The base pairs are known as adenine (A), guanine (G), cytosine (C) and thymine (T). Two base pairs always connect. A connects with T, and G connects with C. The cell translates the order of these base pairs into proteins, which facilitate the functions of the cell.
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Chromosomes
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All DNA is tightly packed into a structure called a chromosome. These chromosomes are named after their shape; the female chromosome looks like an X, and the male sex chromosome looks like a Y. Chromosome count may vary depending upon the species. Humans have 46 chromosomes, which is actually a pair of 23 chromosomes. One set is inherited from the mother, and the other set is inherited from the father. A location on a chromosome is known as a locus (plural is loci).
DNA Fingerprinting
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Humans share approximately 99.9 percent of all DNA with each other, which is equal to about 3 million base pairs. When it comes to DNA fingerprinting, researchers try to look for multiple regions of high divergence loci. For economic and time-related reasons, only parts of the DNA are tested. There may be a chance that two people share the same sequences at one region, but some tests require as many as 13 loci. At that point, the odds that two people share a match are only at about one in a billion, according to the Oak Ridge National Laboratory.
Mitochondria
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Besides the nucleus, the mitochondria also contains DNA. The mitochondria is kind of like the powerhouse of the cell because it has a major role in the production of energy. It is believed that the mitochondria was once a separate organism that became integrated into the eukaryote cell during the course of its evolution (the chloroplast, the site of the plant cell that is responsible for photosynthesis, also has its own DNA). Mitochondrial DNA is passed on by the mother. Though there is relatively little mitochondrial DNA, it can be tested in a similar way nuclear DNA is tested to identify individuals.
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References
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