Extrachromosomal inheritance in Schizosaccharomyces pombe. VII. Studies by zygote clone analysis on transmission, segregation, recombination, and uniparental inheritance of mitochondrial markers conferring resistance to antimycin, chloramphenicol, and erythromycin.

Crosses involving mitochondrial markers conferring resistance to antimycin (anar, AR), chloramphenicol (capr, CR), and erythromycin (eryr, ER) in cis- and trans-configuration were studied by zygote clone analysis. Mutant anar-8, from which all other drug--resistant isolates were derived, exhibits a highly biased transmission (6.8% anar) in an analysis of 100 individual zygote clones. Important results of zygote clone analyses were:--Zygote clones may contain one, two, three, or four mitochondrial genotypes.--The proportion of the two parental and the two recombinant genotypes in individual zygote clones can vary almost over the entire range of percentages.--Proportions of the two corresponding recombinant types in individual clones are usually unequal.--Transmission rates of markers are higher in trans- than in cis-crosses, indicating additivity of bias by two mutated alleles in coupling.--Transmission rates are different for the three markers both in cis- and trans-crosses, being lowest for CR and highest for ER.--Up to more than 80% uniform clones, expressing only one genotype, can be produced in cis- and trans-crosses. In cis-crosses always the double-sensitive parental type becomes uniform, in trans-crosses this may be the case for parental and/or recombinant genotypes. A tentative map is presented using data from cis- and trans-crosses, including a correction by omission of uniform clones. Phenomena of transmission, segregation, and formation of uniform clones are discussed with special regard to the difference brought about by fission versus budding. A comparison with relevant data from Saccharomyces cerevisiae and other organisms is presented.