Figure 2.

Mutations introduced to the TSM cause chromosome instability. (A) Diploid cells bearing homozygous mutant alleles of histone H3 or H4 were tested for their mating behavior. Cells mate with a tester strain (227a or 70α, see Table 1) acquire the ability to grow in SD minimal medium. Cells containing the R35S mutation in histone H4 are hypersensitive to benomyl and do not affect the tension sensing function. The three WT control strains on the bottom roll are, from left to right, MATα, MATa, and MATa/α. (B) Genomic PCR reveals the stochastic loss of one of the two copies of chromosome III. Cells scraped from the YPD (before mating) patches were subjected to DNA isolation and PCR, using primers amplifying both silent mating loci concomitantly. The corresponding mating behaviors of each patch on YPD and SD plate are shown below each lane of the DNA gel. The relative intensity of the two mating loci PCR products correlates with the mating ability. (C) FACS analysis of the DNA content of asynchronous diploid strains before and after mating. Successful mating increases the DNA content. The G1 peak of the WT and each mutant diploid is marked by a broken and a solid vertical line, respectively. The right shift of the G1 peak after mating is indicated by arrows.