Determination of Chromosome Ploidy in Yeast

Wild-type and industrial strains of Saccharomyces cerevisiae appear to be typically polyploid/aneuploid. Such strains are also essentially sterile, but will on rare occasions produce spores. The mating of such spores with reference laboratory strains can be used to give a general estimation of the overall ploidy level. Similarly, measurement of a parameter that is proportionally maintained relative to ploidy level in a euploid reference series, such as DNA content or a certain enzyme activity, can be used to estimate the general overall ploidy of wild-type or industrial strains (1 ,2 ). However, this does not take account of interstrain variability and, in particular, aneuploidy.