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Allele variation and gene function.docx
Allele variation and gene function.docx

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University of Guelph
BIOL 1090
Andrew Bendall

Allele variation and gene function November 26 2012h  Genes may (and usually) have more than 2 alleles  Different alleles may affect the phenotype in different ways  A single gene may control several traits  Multiple genes may control a single trait Genes usually have more than 2 alleles  The most common allele is considered the wild type  Designated with a superscript + (e.g. A+ or C+)  Any allele found at appreciable frequencies  Any allele found at appreciable frequencies (at least 1%) in the populations is considered to be a polymorphism  All other alleles are considered as mutants Why are certain alleles dominant or recessive?  Recessive mutations almost always involve loss of gene function  Complete loss of function (null allele)  Partial loss of function (hypomorphic allele)  Loss of function mutations are usually recessive because, for most genes, one functional copy is enough for a normal (wild type) phenotype What makes an allele dominant or recessive?  Dominant mutations can involve a loss of function or a gain of gene function  Loss of function mutation for those genes for which one functional copy is not enough (haploinsufficiency)  Dominant negative mutation a loss of function mutation that interferes with the the normal function of the wt allele  Gain of function
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