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Figure 5.9 Segregation pattern for a cross reciprocal translocation (black centromeres) X normal sequence (white centromeres). From Perkins (1974). With permission from Genetics Society of America.

genes in the same biosynthetic pathway are not generally linked or clustered. Another fact learned from the mapping work is that crossover frequencies, while reproducible in crosses with the same two parents, vary widely in crosses with parents of different genetic backgrounds. The gene maps showed also that most genes related to the sexual cycle are not linked to the mating type locus (idiomorphs).

Figure 5.10 A partial gene map of linkage group VR. Abbreviations of genes: cyh-2, cycloheximide resistant-2; his-1, histidine-1; sen, senescent; al-3, albino-3; pab-1, para-aminobenzoic acid-1. One map unit (mu) = 1% recombination between gene loci.

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