DNA-LENGTH POLYMORPHISMS OF CHROMOSOME-III IN THE YEAST SACCHAROMYCES-CEREVISIAE

The chromosome-sized DNAs of sporulation-deficient mutants, which had been isolated by mutagenizing spores of a homothallic diploid strain ( MT98a-3D) of Saccharomyces cerevisiae, were analyzed by pulsed-field g el electrophoresis. While the size of chromosome III DNA of the parent strain was 450 kb, some mutants had one or more chromosome III DNAs o f 350 kb, 450 kb, 530 kb and 630 kb. No size variation was observed fo r other chromosomes. Chromosome III DNAs of laboratory-stock strains, except MT98a-3D, were in the neighborhood of 350 kb. Size variation of chromosome III was observed at a high frequency in spore clones deriv ed from MT98a-3D strain. The results suggest that DNA-length polymorph isms of chromosome Ill are generated by the loss or addition of a spec ific DNA unit of approximately 100 kb.