Ordered Linear Tetrads Are Produced by the Sporulation of Newly Formed Zygotes of Saccharomyces cerevisiae.

Diploid Saccharomyces cerevisiae strains normally sporulate to produce tetrahedral unordered asci containing four spores (tetrads). We report that when newly formed zygotes are subjected to the same sporulation conditions, they form predominantly linear ordered tetrads. We show that the two spores from each end of such a linear tetrad invariably contain nonsister centromeres. Spore viability, recombination and independence of centromere segregation appear unaffected.