Genetic analyses of "paranoiac" mutants of Paramecium tetraurelia

Abstract

Six mutants of Paramecium tetraurelia with curious "Paranoiac" phenotypes have been isolated and examined. Instead of the normal transient avoiding reactions in Na+ solution, these mutants show "violent avoidances"--backing continuously for 10 to over 60 sec. This behavior corresponds to prolonged membrane excitation excitation.--Genetic analyses establish five genic loci at which mutations give the "Paranoiac" phenotype. Close linkage between two of these genes occurs. Allelic variants are found for two of the genes. In one case, the two alleles determine very different behavioral phenotypes ("Paranoiac" and "fast-2"). These results show that the mechanism(s) which shuts off excitation in the wild-type membrane is (are) complex, but in the future may be fruitfully pursued in mutants which are defective.