Retention of cytoplasmic killer determinants in yeast cells after removal of mitochondrial DNA by ethidium bromide

Summary The killer character in yeast shows cytoplasmic inheritance. Killer cells were treated with ethidium bromide and their DNA subsequently examined by caesium chloride density gradient centrifugation. Under conditions in which more than 94% of detectable mitochondrial DNA is lost, more than 99% of the cells retain the killer phenotype. It is concluded that the killer genetic determinants are unlikely to be part of the mitochondrial genome.