Recently, it was demonstrated that Candida albicans contains mating type genes. Since that discovery, it has been demonstrated that the majority of strains contain both a and "[agr ]" a genes, that a minority are homozygous for a or "[agr ]" and can undergo fusion, and that the cytological stages of fusion and zygote development are similar to the stages of mating in Saccharomyces cerevisiae. However, it has recently been demonstrated that in order to mate, homozygous a and homozygous "[agr ]" cells must undergo phenotypic switching from the white to opaque phase, adding a developmental step to mating that might be related to pathogenesis.