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.