‘Diad Analysis’ for Linkage Study in Yeast with Poor Spore Viability

Equations were derived expressing the expected frequencies of the parental ditype (PD), non-parental ditype (NPD) and tetratype (T) as a function of the frequencies of 10 diad types with two spores from double heterozygous diploids. Using these equations, a novel procedure, ‘diad analysis’ was proposed that permits the estimation of centromere linkage from the frequencies of 10 diad types with two spores. To test the applicability of the diad analysis, the expected numbers of PD, NPD and T asci were calculated using these equations with simulated data for the 10 diad types, taken from tetrad data, and the results were compared, by x 2 statistics, with the observed data from the same tetrads. A good fit was found between the two. A comparison of diad analysis with tetrad analysis and random spore analysis is also discussed.