Analysis of X-gal plates for quantitative plasmid stability determinations in Saccharomyces cerevisiae

Summary X-gal plates were evaluated for the measurement of plasmid stability in yeast cells carrying the Escherichia coli lacZ gene. The influence of the medium, cloned gene number, and cell state on the accuracy of the results was determined by comparison with traditional replica plating. With few exceptions, X-gal plates provide a good quantitative one-step assay for plasmid stability in Saccharomyces cerevisiae expressing -galactosidase.