Cryptic heterokaryons in Saccharomyces cerevisiae strains: Model experiments

Heterokaryons capable of segregating clones of different phenotypes were ob tained in saccharomycetes yeast. Clones expressing phenotypic traits encode d by the nuclear genome of one parent and the mitochondrial genome of anoth er were shown to contain cells that carried the second phenotypically silen t nucleus. The cryptic nucleus can be uncovered by growing these "cytoducta nts" on the corresponding medium. The use of strains carrying an insertion in the URA3 gene and the endogenic plasmid, 2 mu m DNA, made it possible to detect this nucleus by blot hybridization.