Fig. 1.

Several mechanisms by which additional chromosomal rearrangements or mutations may facilitate correction of an inherited recessive genetic disorder. The yellow and blue bars indicate an individual gene, with black hashes indicating a disease-causing mutation. Reversion mutations may arise either during or subsequent to DNA replication and may involve transfer of genetic material between paired chromosomes (gene conversion or intragenic crossover) or mutations within a single chromosome (and gene). Gene conversion, intragenic crossover, and back mutations result in genetic correction in one allele within a daughter cell (indicated by the green border and background). Second-site mutations (white hash) result in a gene capable of generating a functional protein (indicated by the green dashed border and green background) in one allele, although the gene itself may differ from wildtype. Adapted from Pasmooij et al. [17]