Isolation and characterization of chromosome-gain and increase-in-ploidy mutants in yeast
Chan, C.S.; Botstein, D.
Genetics 135(3): 677-691
1993
ISSN/ISBN: 0016-6731 PMID: 8293973 Document Number: 415587
We have developed a colony papillation assay for monitoring the copy number of genetically marked chromosomes II and III in Saccharomyces cerevisiae. The unique feature of this assay is that it allows detection of a gain of the marked chromosomes even if there is a gain of the entire set of chromosomes (increase-in-ploidy). This assay was used to screen for chromosome-gain or increase-in-ploidy mutants. Five complementation groups have been defined for recessive mutations that confer an increase-in-ploidy (ipl) phenotype, which, in each case, cosegregates with a temperature-sensitive growth phenotype. Four new alleles of CDC31, which is required for spindle pole body duplication, were also recovered from this screen. Temperature-shift experiments with ipl1 cells show that they suffer severe nondisjunction at 37 degree . Similar experiments with ipl2 cells show that they gain entire sets of chromosomes and become arrested as unbudded cells at 37 degree . Molecular cloning and genetic mapping show that IPL 1 is a newly identified gene, whereas IPL2 is allelic to BEM2, which is required for normal bud growth.