Figure 4.

Complex cases of intron boundary evolution. A. Intron 5 of CNM00170. Both boundaries of the intron in JEC21 are non-conserved, however the presence of gaps inducing frameshifts suggests that the region is intronic across all species. B. Intron 1 of CND00470. Only WM276 shares the JEC21 5' intron boundary, suggesting either convergent intronization in JEC21 and WM276 or convergent loss of splicing in the other two species. C. Intron 5 of CNM00170. The 5' intron boundary is not conserved, and there is no nearby alternative candidate boundary, however the presence of coding frame-interrupting indels suggests that the sequence is ancestrally intronic.