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A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. One such family are the genes for human hemoglobin subunits; the ten genes are in two clusters on different chromosomes, called the α-globin and β-globin loci. These two gene clusters are thought to have arisen as a result of a precursor gene being duplicated approximately 500 million years ago.
Genes are categorized into families based on shared nucleotide or protein sequences. Phylogenetic techniques can be used as a more rigorous test. The positions of exons within the coding sequence can be used to infer common ancestry. Knowing the sequence of the protein encoded by a gene can allow researchers to apply methods that find similarities among protein sequences that provide more information than similarities or differences among DNA sequences.
If the genes of a gene family encode proteins, the term protein family is often used in an analogous manner to gene family.
The expansion or contraction of gene families along a specific lineage can be due to chance, or can be the result of natural selection. To distinguish between these two cases is often difficult in practice. Recent work uses a combination of statistical models and algorithmic techniques to detect gene families that are under the effect of natural selection.
The HUGO Gene Nomenclature Committee (HGNC) creates nomenclature schemes using a "stem" (or "root") symbol for members of a gene family, with a hierarchical numbering system to distinguish the individual members.
- Nussbaum, Robert L.; McInnes, Roderick R.; Willard, Huntington F. (2016). Thompson & Thompson Genetics in Medicine (8th ed.). Philadelphia, PA: Elsevier. p. 25. ISBN 978-1-4377-0696-3.
- Hartl, D.L. and Clark A.G. 2007. Principles of population genetics. Chapter 7, page 372.
- Demuth, Jeffery P.; Bie, Tijl De; Stajich, Jason E.; Cristianini, Nello; Hahn, Matthew W.; Borevitz, Justin (20 December 2006). "The Evolution of Mammalian Gene Families". PLoS ONE 1 (1): e85. doi:10.1371/journal.pone.0000085.
- Daugherty, LC; Seal, RL; Wright, MW; Bruford, EA (Jul 5, 2012). "Gene family matters: expanding the HGNC resource.". Human genomics 6 (1): 4. doi:10.1186/1479-7364-6-4. PMC 3437568. PMID 23245209.
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