Saccharomyces cerevisiae expression data, adapted fromHolstege et al. (1998)
| Nonribosomal | Ribosomal-protein | |
| No introns | 5.17 | 91.9 |
| With intron | 17.6 | 91.7 |
| Minimal intron | Nonminimal intron |
[i] We classify the genes in two ways: based (1) on whether they are ribosomal-protein or nonribosomal genes and (2) on whether or not they have any introns. Ribosomal-protein genes tend to have nonminimal introns, and nonribosomal genes tend to have minimal introns. The 2 × 2 grid shows the averaged mRNA synthesis rate for those genes in each of the four categories.