To achieve coordinate gene regulation, yeast (Saccharomyces cerevisiae) appears to have exploited two distinct multifunction "operon" schemas: one, by concatenating originally separate functional domains into single polypeptides, and two, by linking opposite strand genes through common promoter elements. For example, distinct functions found in bacterial operons are often concatenated in yeast. A selective advantage, similar to that for bringing multiple related functions into a single peptide, may also explain the large numbers of yeast opposite-strand, ORF pairs sharing a common regulatory region.