Term used in genetics. Base analogs are mutagenic chemicals that can serve as substitutes for purines or pyrimidines in nucleic acid biosynthesis. Base analogs are very similar to the bases in DNA, often differing from them only in one active group.
Due to the similarity of their structure, base analogs can be incorporated into the DNA during replication and thus alter the genetic material of a cell. For example, the base analog 5-bromouracil (5BU) is almost identical to the base thymidine and can be incorporated into the DNA instead of thymine. It binds with adenine as a complementary base.