ABSTRACT
Mutant strain d48 of Paramecium tetraurelia lacks the gene for antigen A in the macronucleus, whereas this gene is present in the micronucleus. Transfer of macronucleoplasm from the wild type to strain d48 caused d48 to revert to the wild type after autogamy. Transfer of cytoplasm was not as effective as transfer of macronucleoplasm. It was also found that the micronucleus of d48 developed normally when it was transplanted to wild-type cells, whereas the micronucleus of the wild type formed a macronucleus that lacked the antigen A gene when this micronucleus was transplanted into d48. It was concluded that the micronucleus of d48 has a normal antigen A gene and that the hereditary determinants responsible for the d48 trait are located in the macronucleus. Molecular analysis of d48 clones that had been induced to revert to the wild type revealed that they possessed the antigen A gene in the macronucleus.
