Mitochondrial recombination in crosses of iso- and anisomitochondrial Saccharomyces cerevisiae.

Mitochondrial mutants resistant to erythromycin, neomycin and monomycin were isolated. Mitochondria were transmitted from different natural strains to the cells of the same nuclear genotype. In bifactorial crosses of such isochromosomal and anisomitochondrial yeasts we tested random samples of diploid colonies. The distribution of mitochondrial markers in parent and recombinant classes has been shown to occur unequally. The asymmetry of parent and the polarity of recombinant classes were observed to differ in different mitochondrial mutants. Anisomitochondrial strain crosses proved that mitochondrial origin essentially influenced both the parent and recombinant classes distribution and the susceptibility of the transmission to the effect of mating type locus. One can distinguish between 'homo- and heterosexual' cross combinations in terms of recombination polarity. The new type of mitochondria was found to occur with high frequency of transmission to the zygote progeny of markers resistant to erythromycin but not of markers resistant to neomycin. The problem of 'sex' in mitochondria is discussed.