Karyotypic Determinants of Chromosome Instability Figure 1. Isolation and karyotype analysis of aneuploid spore colonies after triploid meiosis. (A) Schematic representation of the experimental design used to follow karyotype changes in freshly generated aneuploid strain populations that resulted from triploid meiotic progeny. The g20 population sample was used to determine the original karyotype of the aneuploid spore that seeded the colony. Black dots represent colonies; red circles indicate the 11 randomly chosen colonies resulted from plating the population culture at different generations, which were used to determine the karyotype variation within the population. (B) Distribution of the apparent ploidy based on FACS analysis of the g20 population samples of the collected aneuploid strains as represented in (A). Red bars represent the expected apparent ploidy distribution by simulating random segregation of homologs during meiosis I of the triploid strain. Black bars represent the apparent ploidy distribution obtained experimentally. Error bars represent standard deviations from 10,000 independent simulations. (C–D) Representative DNA content profiles by FACS (upper panels) and chromosome copy numbers by qPCR (lower panels) of two aneuploid strains, for which the original karyotype was directly determined from the g20 population data (C) or indirectly inferred from colony data, i.e. from the most commonly observed copy number across the analyzed colonies (D). PLoS Genetics | www.plosgenetics.org 3 May 2012 | Volume 8 | Issue 5 | e1002719