Density Changes of Cytoplasmic DNA fromPetiteMutants ofSaccharomyces Cerevisiaeand a Hypothesis on the Mechanism of the Mutation

Abstract

Abstract The purpose of this paper is to show new data on the nature of cytoplasmic mutation which leads to respiratory deficiencies in yeast. The satellite DNA density of two new strains obtained by treatment with acriflavin and U.V. rays, has been examined in CsCl density-gradient. In all cases the density appeared to be less than in the wild-type. It has also been shown that a respiratory-deficient strain, further treated with acriflavin, can show a further shift of the position of the satellite band, always in the sense of a reduction of density. Also from the ϱ+ × ϱ- cross, ϱ- strains can be recovered in which the density of the satellite band is less than the density of the parent ϱ- strain. This fact suggests the existence of recombination among cytoplasmic DNA. On the basis of these observations, the hypothesis has been formed in which the cytoplasmic mutation derives from the premature detachment of the DNA polymerase from its template.