question: Which eukaryote genomes contain operons?
answer: Genes in nematode and ascidian genomes frequently occur in operons such genes comprise 15-20% of the coding genome for Caenorhabditis elegans and Ciona intestinalis We find that birth-death models of operon evolution reasonably describe the relative abundance of operons of different sizes in the C. elegans and Ciona genomes and generate predictions about the number of monocistronic, nonoperon genes that likely participate in the birth-death process