Chromosomal organization of and distance between the MAT-1 and MAT-2 loci.  The two lines represent the genomic organization of the MAT loci .  The distance between the a and b gene complexes is 500-kb for MAT-1 and 430-kb for MAT-2.  The triangles represent inserts of plasmid constructs used to tag the respective mating-type loci.  The mfa, pra, bE and bW open reading frames are shown as arrows indicating the direction of transcription. Ethidium bromide stained CHEF gel electrophoresed for 48 hr. and a DNA gel blot of the same gel hybridized with a b gene probe. Lanes:  1, I-SceI digested wild-type strain 364 (a1b1); 2, I-SceI digested 364-86 (a1b1; single tag at a1); 3, undigested 364-86dt21 (a1b1;  double tag at a1, b1);  4, I-SceI digested 364-86dt21(a1b1;  double tag at a1, b1);  5, I-SceI digested 365-57dt51 (a2b2;  double tag at a2, b2);  6, undigested 365-57dt51 (a2b2;  double tag at a2, b2);  7, I-SceI digested 365-57 (a2b2; single tag at b2);  8, I-SceI digested wild-type strain 365 (a2b2). See Lee et al. 1999