52316.1 Forward genetics16.1 Forward geneticsTypically, forward genetics starts with the wild-typegenome, mutates it randomly with a mutagen, and sys-tematically surveys it for mutations that share somecommon phenotype. This procedure is sometimes calleda mutant hunt. Ideally, we will identify mutations in lit-erally all the genes in the genome that can be mutatedto a state that confers that particular phenotype. Thenwe can say that we have saturatedthe genome for muta-tions of that class. In reality, it is very difFcult to achievetotal saturation—for several reasons. Typically a muta-gen has a low, more or less equivalent probability of mu-tating any region of the genome. However, the sizes ofgenes within a species can vary considerably. The largerthe size of the gene, the greater is the mutagen’s target,and the more likely it is that a mutation will be pro-duced in it. ±urthermore, because mutations are oftenpleiotropic (have numerous effects on the phenotype), itis possible that a mutation’s more severe effect—such ascausing death during development—might mask itsmilder manifestations, such as altering adult hair color.
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.