Genetic Analysis O F Polyploid Yeast

HE yeast Saccharomyces cerevisiae normally alternates between haploT phase and diplophase, propagating vegetatively primarily as a diploid (WINCE 1935). SUBRAMANIAM and coworkers ( SUBRAMANIAM and KRISHNA MURTHY 1949; MITRA and SUBRAMANIAM 1949 ; SUBRAMANIAM 1951) have reported the production of tetraploids by the exposure of diploid yeast to acenaphthene and chrysene. Their data lack any genetic support. ROMAN, HAWTHORNE and DOUGLAS (1951) have described a single aberrant ascus, which they suggest might have arisen from a tetraploid. A genetic analysis of tetraploids produced by mass mating of diploid gametes (LINDEGREN and LINDECREN 1951 ) was obscured by uncontrolled sporulation of the diploids arising from the tetraploids. These workers also report the production of a triploid, but present no genetic data for this culture. The isolation of triploid and tetraploid clones by means of a prototroph recovery procedure has been reported (POMPER 1952a, b). This paper will describe some of the results of genetic analyses carried out on triploid and tetraploid c b n ~ of S. cerevisiae.