SACCHAROMYCES CEREVISIAE PETITE MITOCHONDRIAL DNA OF SUPPRESSIVE AND NEUTRAL HAPLOIDS AND OF [rho−] DIPLOIDS OBTAINED FROM CROSSING [rho+] TO A NEUTRAL PETITE
An unusual property of GR25a [rho+] was the production of 20 to 30 percent [rho−] zygote colonies when crossed to a tester strain lacking mitochondrial DNA. Spontaneous [rho−] isolates of GR25a [rho+] were observed to be highly suppressive and to contain mitochondrial DNA of a parental buoyant density (1.685 g/cm3). Three ethidium bromide induced neutral petites of GR25a [rho+] did not have detectable mitochondrial DNA and were neutral in crosses to [rho+] strains. Seven [rho−] zygote colony isolates obtained from crossing GR25a [rho+] to a neutral petite were shown to contain abnormal mitochondrial DNA. Six zygote colony isolates had mitochondrial DNA of a buoyant density less than, or equal to, GR25a (1.682–1.685 g/cm3), whereas one isolate had a buoyant density greater than GR25a (1.688 g/cm3). It was suggested that abnormal mitochondrial DNA is generated during the mating reaction.