Mating type gene
genes that, in saccharomyces cerevisiae specify into which of the two mating types (a and _) a particular cell falls. Only unlike mating type haploids will fuse. The interest derives from the way in which mating type is switched, the existing gene is removed and a new gene, derived from a (silent) master copy elsewhere in the genome is spliced in. Later this gene will in its turn be replaced by a new copy of the old gene, also derived from a silent master. The a and _ genes code for pheromones that affect cells of the opposite mating type. Similar mating type genes are known from other yeasts and the switching mechanism (cassette mechanism) may be used more generally.