a, Sequence logos of 5′ splice sites, 3′ splice sites, ratchet points, and non-ratchet point AG/GT sequences located in the same introns as ratchet points (top to bottom). b, Sequence conservation of ratchet points. Average PhastCons scores of ratchet points (green) and non-ratchet points (blue). Solid line indicates the average PhastCons score, shaded regions indicate the 95% confidence interval. Normalized recursive junction (c) reads and percent non-recursive junctions (d) observed in untreated S2 cells and cells treated with the indicated dsRNAs.