A rapid isotope dilution procedure for estimating the relative proportion of mitochondrial DNA in yeast

A method is described for estimating rapidly the relative proportion of total DNA that is of mitochondrial origin in small quantities of the yeast, Saccharomyces cerevisiae. This procedure involves the mechanical disruption of cells followed by the addition of small amounts of radioactively labeled yeast nuclear and mitochondrial DNA to the lysate. Both labeled and unlabeled DNAs are then co-extracted from the mixture and separated into nuclear and mitochondrial DNA components by poly(l-lysine) Kieselguhr column chromatography. The resulting specific radioactivities of each species of DNA, when compared to the amount of labeled DNA initially added, are related to the relative proportion of unlabeled nuclear and mitochondrial DNA in the original cell sample. The isotope dilution procedure reported here is shown to be both reproducible and to reflect the true relative concentrations of each species of DNA in this yeast.