Genetic differences between Saccharomyces carlsbergensis and S. cerevisiae II. Restriction endonuclease analysis of genes in chromosome III

Abstract

Chromosome III in a haploid Saccharomyces cerevisiae strain has been previously substituted for by its homeologue from S. carlsbergensis. With this chromosome substitution line the two homeologous chromosomes were shown to undergo crossing over only in a limited region, and to differ in nucleotide sequence at theHIS4 locus. In the present study the S. carlsbergensis chromosome III was compared to its S. cerevisiae homeologue at several additional loci. Cloned DNA from the S. cerevisiae lociHML, HIS4, LEU2, MAT andSUP-RL1 was used as hybridization probes in the analysis of nucleotide sequence homology at these loci andHMR. Virtually no differences were detected atSUP-RL1 andHMR, located in the region where the two chromosomes recombine, whereas considerable differences were found in the non-recombining part. The data are consistent with the assumption thatHML, MAT andHMR of the S. carlsbergensis chromosome are organized as in S. cerevisiae Segments X and Z1, which are involved in mating type interconversion, were closely homologous to their S. cerevisiae counterparts, whereas Y α as well as sequences outside theHML andMAT cassettes were substantially different.