Fig. 1. Disruption of CIR1 in the MATa strain was confirmed by Southern blot analysis. Restriction maps of the genomic regions containing the wild-type or the disrupted CIR1 allele are shown. Genomic DNA of the serotype D MATa strain (JEC20) was digested with BamHI/HindIII and hybridized with the probe indicated. Lane 1 contains DNA from the serotype D wild-type strain JEC20. Lanes 2 and 4 contain DNA from the cir1 mutant strains and show that the disruption cassette integrated at the CIR1 locus. The mutants represented by lanes 2 and 3 were designated as cir1Δ#7 and cir1Δ#37, respectively. Lane 3 contains DNA from a transformant that has an ectopic integration of the disruption cassette.