(Science: biochemistry) a chemical which resembles a nucleotide base. They can substitute the purine and pyrimidine bases that normally appear in dna, despite minor differences in structure. May be used for inducing mutations, including point mutations.
For example: 5 bromouracil can replace thymine or 2 aminopurine replace adenine. A foreign chemical that mimics the complimentary pairing of a genetic sequence, and usually proves to be a mutagen. This is because the base analogue harnesses the information on that particular [[