Individual Genetic Variation - Research Article from Macmillan Science Library: Genetics

This encyclopedia article consists of approximately 3 pages of information about Individual Genetic Variation.
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Variation and Alleles

Any locus having two or more alleles (variant forms of particular genes), each with a frequency of at least 1 percent in the general population, is considered to be polymorphic. The difference between two alleles may be as subtle as a single base-pair change, such as the thymine-to-alanine substitution that alters the B chain of hemoglobin A from its wild type to its hemoglobin sickle cell state. These single nucleotide polymorphisms are termed "SNPs" ("snips").

As of March 2002, in the approximately 3.2 billion base pairs of DNA, approximately 3.2 million SNPs have been identified. Some base-pair changes have no deleterious effect on the function of the gene; nevertheless, these functionally neutral changes in the DNA still represent different alleles. Alternatively, allelic differences can be as extensive as large, multi-codon deletions, such as those observed in Duchenne muscular dystrophy.

This woman has the inherited trait that allows her to roll her tongue. This woman has the inherited trait that allows her...

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This section contains 668 words
(approx. 3 pages at 300 words per page)
Buy the Individual Genetic Variation Encyclopedia Article
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Macmillan Science Library: Genetics
Individual Genetic Variation from Macmillan Science Library: Genetics. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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