Molecular and genetic analysis of chromosomes X in Saccharomyces carlsbergensis

Abstract

Molecular hybridization of electrophoretically separated and blotted chromosomes withILV3 gene probes detected the presence of three chromosomes X in S. carlsbergensis 244 lager yeast. Meiotic segregants, which were disomic or trisomic for chromosome X were crossed with akar1-1 strain of S. cerevisiae (MATa orMAT aarg3 met3 ilv3 cyc1-1 cdc11 hom6 ade2-40 cyh2 kar1-1) for single chromosome transfer and isolation of two of the chromosomes X from the lager yeast. Type I chromosome X migrates slower than a reference chromosome X of S. cerevisiae K5-5A during chromosome separation by electrophoresis and contains the allele ofILV3 unique to the lager yeast. It recombines with chromosome X from S. cerevisiae, but only in the left arm. Type II chromosome X migrates faster than the reference chromosome X and contains the allele ofILV3 also found in S. cerevisiae S288C. It recombines only in the right arm with chromosome X from S. cerevisiae. The third chromosome X from S. carlsbergensis, which co-migrates with the reference chromosome X of S. cerevisiae K5-5A, has yet to be isolated into the genetic background of a genetic standard strain.