['We investigated the determinants of sexual identity in the budding yeast Saccharomyces cerevisiae. The\xa0higher fungi are divided into the ascomycetes and the basidiomycetes. Most ascomycetes have two mating types: one (called α in yeasts and MAT1-1 in filamentous fungi) produces a small, unmodified, peptide pheromone, and the other (a in yeasts and MAT1-2 in filamentous fungi) produces a peptide pheromone conjugated to a C-terminal farnesyl group that makes it very hydrophobic. In the basidiomycetes, all pheromones are lipid-modified, and this difference is\xa0a distinguishing feature between the phyla. We asked whether the asymmetry in pheromone modification is required for successful mating in ascomycetes.', 'We cloned receptor and pheromone genes from\xa0a filamentous ascomycete and a basidiomycete and expressed these in the budding yeast, Saccharomyces cerevisiae, to generate novel, alternative mating pairs. We find that two yeast cells can mate even when both cells secrete a-like or α-like peptides. Importantly, this is true regardless of whether the cells express the a- or α-mating-type loci, which control the\xa0expression of other, sex-specific genes, in addition to the pheromones and pheromone receptors.'] Is asymmetry in sexual pheromones required for ascomycete mating?