Detection of specific DNA sequences in yeast by colony hybridization

A procedure is described for the detection of specific DNA sequences in Saccharomyces cerevisiae. This method allows a rapid screening of a large number of yeast colonies. The yeast cells of each colony, grown on nitrocellulose filters, are converted, in situ, to protoplasts by snail enzyme, and are then lysed and their DNAs are denatured and fixed on the filter. The presence of the specific DNA sequence is detected directly on the filter by hybridization with a radioactive cRNA. We have used successfully this technique to detect the presence or the absence of specific mt DNA sequences in p+, p- and p0 strains, and to detect the presence or the absence of the 2 mum DNA sequences in different strains.