S: (n) reversion ((genetics) a return to a normal phenotype (usually resulting from a second mutation))
S: (n) saltation ((genetics) a mutation that drastically changes the phenotype of an organism or species)
S: (n) deletion, excision, cut (the omission that is made when an editorial change shortens a written passage) "an editor's deletions frequently upset young authors"; "both parties agreed on the excision of the proposed clause"
S: (n) deletion (the act of deleting something written or printed)