Introduction to Genetic Analysis 538

Introduction to Genetic Analysis 538 - is whether the...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: is whether the mutation represents a loss of function or a gain of function . Recessive mutations are generally loss- of-function alleles of a haplosufficient gene. Indeed most mutations are of this type. Dominant mutations are more diverse but often more interesting, and special tests are needed to distinguish dominant mutations that represent a loss of function from those that represent a gain of function. Let’s consider dominant mutations (Figure 16-22). Consider a dominant null mutation. In that case, a single copy of the wild-type allele does not make enough gene product to generate a wild-type phenotype. Hence if a gene generates a loss-of-function dominant mutation, we can infer that it falls into the class called haploinsuffi- cient. We can recognize such a mutation by comparing the 1 /M phenotype first with the phenotype produced by a deletion 1 / D , if available, and then with the pheno- type produced by a duplication Dup/ M (see Figure 16-22a). First, the phenotype of a mutant gene paired with a wild-type gene should be the same as the pheno- type shown by a deletion. Second, the dominant mutant phenotype should be “cured” by adding a duplicate copy of the wild type. Loss of function is not always 100 percent; it can be at some intermediate level. Some loss-of-function muta- tions completely eliminate the activity of the gene prod- uct (null mutations; Figure 16-22a). Others merely de- crease the activity of the gene product; these are called...
View Full Document

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.

Ask a homework question - tutors are online