Three types of mutagenesis

Mutagenesis is typically the result of modification of a base in one strand, so as to alter the correct pattern of base pairing with the alternate strand. Mutagenic events include (A) incorporation of a none-base but base-like substance during DNA replication, (B) chemical alteration of a base so as to change its base pairint, or (C)  alteration of bases in an oxidizing / reducing cellular environment.

Figure © 2012 TA Brown, Introduction to Genetics (1st ed.); additional text © 2012 by Steven M. Carr