Schematic representation of RNA repair using a trans-splicing ribozyme. A Group I ribozyme delivers corrective sequences (3′ exon) to a mutant transcript. The ribozyme binds upstream of the mutation through base-pairing. Once bound, the ribozyme cleaves the target RNA, releases the downstream cleavage product, and splices the 3′ exon sequence onto the upstream cleavage product. M, mutant sequence; W, wild-type sequence corresponding to the mutated region.