Polymorphisms - Research Article from Macmillan Science Library: Genetics

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Coding and Noncoding Sequences

The amino acid sequence of proteins is directed by the information found in genes, which in turn are made up of DNA. Genes that have different DNA sequences are said to be polymorphic. These different gene forms are called alleles, exemplified by the alleles that control eye color. When alleles result in differences in the amino acid sequence of a protein, the proteins encoded by alleles are called isoforms. The position of the gene on a chromosome is its locus (plural, loci). More generally, a locus refers to any position on a chromosome, whether or not a gene is located there.

Polymorphisms arise through mutation. The mutation may be due to a change from one type of nucleotide to another, an insertion or deletion (collectively known as indels), or a rearrangement of nucleotides. Once formed, a polymorphism can be inherited like any other DNA sequence...

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This section contains 1,398 words
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Macmillan Science Library: Genetics
Polymorphisms 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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