AGENTS THAT CAUSE A HIGH FREQUENCY OF GENETIC CHANGE FROM [psi +] TO [psi -] IN SACCHAROMYCES CEREVISIAE

The [psi] factor of yeast is cytoplasmically inherited. Singh, Helms and Sherman (1979) reported that high concentrations of KCl and of ethylene glycol induce the genetic change from [psi  +] to [psi  -]. In this study, the following agents have been shown to induce the same genetic change: guanidine hydrochloride at 1 mm, dimethyl sulfoxide at 2.5% v/v and ethanol or methanol at 10% v/v. It is likely that a number of other agents also cause the change, namely 2 m glycerol, m succinate, m glutamate and m MgCl2. Most of these agents induce the change at very high frequencies; with some, the frequency is 100%. Although the observed phenotypic change can also occur as a result of chromosomal gene mutation, no changes of this type were identified. Some of the agents also cause mutation from [rho  +] to [rho  -] and from killer to sensitive.