Segregation analysis of chromosome 3 disome.

(a)P219 (h−leu1 ade6-M210/ade6-M216) was crossed with a haploid strain that was h+ with ade6-M216 (or ade6-M210) and one of the indicated alleles (except not2, which is mapped on chromosome 3). Strain 56-1 (h−leu1 ade6-M210 not2::kan/ade6-M216 not2+) was crossed with h+ade6-M216 not2::kan. Ade+ segregants were selected on an EMM2 plate at 30°C.(b)Ade+ colonies were randomly selected and tested for drug resistance. For the not2 mutant, see (d).(c)All tested 12 Ade+ segregants had the “unstable Ade+” phenotype, indicating a chromosome 3 disome. Note, wild-type did not produce drug-resistant segregants.(d)For this cross, 24 of 26 Ade+ (disomic for chromosome 3) were G-418 resistant. Of these 24 segregants, 15 were homozygous for the not2::kan mutant, while 9 were heterozygous (see Materials and methods).(e)G-418 resistant Ade+ segregants in this mutant were generally small, and upon restreaking on YE plates only stable Ade+ colonies (probably diploids) and Ade− haploid colonies were produced. Chromosome 3 disome was hardly recovered thereafter.