Nuclear Misbehavior in an Aberrant Inbred Tetrahymena*

Abstract

SYNOPSIS. Breeding anomalies in an inbred strain (B1) of syngen 1, Tetrahymena pyriformis , are traced to aberrant chromosomal constitutions of the micronuclei. The origins of the micronuclear defects have not been established, but they probably arise in much the same manner as those observed earlier in “semi‐amicronucleate” clones, except that they occur later and in lower frequencies. The abnormal nuclei are impaired in their ability to carry out the maneuvers required for normal conjugation; some are blocked in MI, most after MII; the occasional cells in which nuclear reorganization is completed have visibly defective macronuclear anlagen and are inviable. When crossed to normal strains, nuclear misbehavior is induced in them and again very few if any viable exconjugants are produced. The details of the aberrations are discussed with reference to the patterns of nucleocytoplasmic interaction in conjugation.