Chapter 12 Induction, Selection, and Experimental Uses of Temperature-Sensitive and Other Conditional Mutants of Yeast

Abstract

This chapter focuses on temperature-sensitive ( ts ) and other conditional mutants of yeast. A conditional mutant is an organism that resembles the wild type under some environmental conditions, but displays a characteristic mutant phenotype under other environmental conditions. The mutation responsible for this phenotype is a conditional mutation. If a conditional mutant is incapable of prolonged vegetative growth under the restrictive conditions, the mutation it harbors is a conditional lethal mutation, and the gene and function that are defective are referred to as indispensable or essential. Various conditional lethal mutants can lose viability (the ability to resume vegetative growth on return to the permissive conditions) at very different rates during a period of exposure to the restrictive conditions. In the chapter, induction and isolation of mutants is discussed and the problem of genetic complexity is explained. Experimental uses of ts mutants are described as well. The study discussed in the chapter is based on experience with Saccharomyces cerevisiae and refers specifically only to that organism.