The answer is; Acridine orange
This mutagen causes an insertion or deletion mutation because it is able to dupe the polymerases enzyme due to its structure that fits in the active site just like nucleic acids. It is thus placed in place of a nucleic acid. During repair and replication, since the polymerase is not able to identify the right base pair to pair with the mutagen, it places any nucleic acid in the complementary strand . The intercalation interferes with the codon sequence (causing it to shift by a base pair) hence causing a frameshift mutation.
