Caryonidal Inheritance and Nuclear Differentiation

Abstract

The following features of caryonidal inheritance in variety 1 of Tetrahymena pyriformis are documented. 1. Cells with the same genetic constitutions may develop different phenotypes, which are inherited during vegetative growth. 2. Mating type diversities which arise at conjugation are distributed approximately at random among the products of the first fission after conjugation. 3. Within a genotype no positive correlation can be detected between the mating type of the parent and the mating type of the progeny. Following Sonneborn, these and previously published observations, both on Tetrahymena and Para-mecium, are interpreted as indicating nuclear differentiation as the basis for mating type determination in these forms. Suggestions regarding the mechanisms of nuclear differentiation and the general significance of such mechanisms are set forth.