HBB and retinitis pigmentosa: By using HDR with a plasmid carrying donor DNA, various mutation patterns have been corrected, including small-sized mutations in the HBB gene (associated with β-thalassemia)30,31,34 and the RPGR gene (associated with retinitis pigmentosa)51, as well as large-sized mutations corrected by the precise knockin of a large DNA fragment from the FVIII gene (associated with hemophilia A)38 and from the DMD gene (associated with DMD)13.