Extra cytoproct mutant inParamecium tetraurelia: a genetical study

Abstract

SUMMARYThe basis of inheritance of the extra cytoproct (XP) character inParamecium tetraurelia, stock d4-154, is shown to be nuclear and probably a single dominant gene,Ec, with reduced penetrance in heterozygotes. When the mutant gene is replaced by its wild-type allele, loss of the XP phenotype in some lines of descent occurs before 15 cell generations, but in more than half of the lines this occurs after 15–120 or more cell generations. The possibility is considered that these extremely long and variable ‘lags’ may be due to extranuclear (cortical) inheritance of cortical changes initially produced by gene action.