Figure 1:
A variety of potential products can be derived from synthesis and processing of a single pre-mRNA, including post-transcriptional RNAs with retained introns. Introns are depicted as thinner black bars spaced between the thicker, colored exons. Co-transcriptional RNAs are elongating, depicted by rightward-facing arrows whereas post-transcriptional RNAs have been cleaved and polyadenylated. Retained introns are often flanked by alternatively spliced exons (orange) compared to constitutively spliced exons (blue).