Genic basis of the mate-killer trait inParamecium aurelia, stock 540

Abstract

1. Stock 540 ofParamecium aurelia(syngen or variety 1) contains two duplicate genesM1andM2, each of which is capable of supporting growth of mu particles in the cytoplasm, thus producing the mate-killer phenotype.2. Of six sensitive stocks ofP. aureliasyngen 1, collected from widely separated localities, none contained eitherM1orM2.3. One sensitive stock (544), though proved to contain both recessive genesm1andm2, gave aberrant ratios of mate-killers and sensitives following hybridization with stock 540. Evidence has been adduced consistent with the hypothesis that them1- andm2-bearing chromosomes are involved in a translocation, by comparison with stock 540.4. There is a proportionality between numbers ofMgenes and speed of killing, and presumably therefore with the number of mu particles.5. Loss of mu particles following substitution ofMgenes by their recessive alleles occurs at times varying between eight and fifteen fissions after change of genotype.