FIG. 2.

Δswi3 mutation reduces mating type switching. (A) The swi3 gene was disrupted by inserting a 1.6-kb kanMX6 cassette between nucleotides +58 and +514 of the ORF; +1 and +546 denote the first and last nucleotides of the swi3 ORF, respectively. (B) Comparison of the iodine-staining phenotype of homothallic wild-type swi3 (SP982), the point mutant swi3-146 (E146), the Δswi3::kanMX6 deletion mutant (BSP61), and a nonswitching Msmt-0 mutant (SP903). Efficiency of mating type switching was monitored by iodine staining of colonies sporulated on PMA medium.