Abstract
Frequent production of respiration-deficient (RD) segregants was observed in the asci of tetraploid bakers'' yeasts. Respiration of bakers'' yeast is controlled by at least 3 complementary genes (R1/r1, R2/r2 and R3/r3)- RD yeasts due to mutation of each of these respiratory genes are characterized by a loss of instability of the cytoplasmic factor necessary for respiration. Te presence of the cytoplasmic factor in the yeasts is stabilized by the existence of dominant genes, R1, R2 (indispensable) and R3.