Kappa, mu and the metagon hypothesis inParamecium aurelia

Abstract

1. The loss of mu 540, mu 138, and kappa 51 following the loss of the dominant genes required for their maintenance was studied. With mu 540 and mu 138 the loss usually occurred within 4–7 cell generations, but occasional cells with mu were found as late as generation 12 with mu 540 and generation 17 with mu 138. Kappa 51 was lost between 5 and 60 fissions in different clones. The variability in time of loss remains unexplained.2. No trail of inheritance of resistance to specific kappa killing comparable to the trail of inheritance reported for mu 540 by Gibson & Beale (1962) was found.3. No loss of kappa 51, mu 540, mu 138, or mu 130 was found following treatment of paramecia with RNase.4.Didinium nasutumwas shown to be able to acquire and maintain kappa 51 when it could not possibly have acquired any RNase-sensitive metagons from paramecia.5. These results show that the metagon hypothesis cannot be accepted without a number ofad hocand at present untestable assumptions.