Figure 4.

Prevalence of single-exon 5'-most genes in Ciona operons. Ratio of genes containing a given number of exons within non-operonic (blue) and operonic (green) gene populations. Red and black lines indicate the ratio within the 5'-most upstream genes encoded in operons and the downstream operonic genes, respectively. Genes with 11 or more exons are not shown in this graph for simplicity. Note that single-exon genes are more prevalent in operons than in the non-operon (monocistronic) gene population, and are especially prevalent among the 5'-most genes of operons.