base analogue


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base analogue

A chemical which resembles a purine or pyrimidine base, which differs slightly in structure from the normal bases found in nucleic acids (DNA or RNA) and, when intercalated in the nucleic acid, may alter one or more of its normal functions or cause point (single-base substitution) mutations.

Examples
Aminopurine (which replaces adenine), bromouracil (which replaces thymine), azaguanine, azauracil, 5-bromodeoxyuridine.

base analogue

Any compound structurally similar to a DNA BASE that can substitute for a base and thus cause a mutation.
Base analogueclick for a larger image
Fig. 62 Base analogue . The action of 5-bromouracil on DNA.

base analogue

any chemical that has a similar structure (i.e. is analogous) to one of the purine or pyrimidine bases in DNA or RNA. Such analogues can become incorporated into the nucleic acid and may act as a MUTAGEN. For example, 5-bromouracil (5Bu) is an analogue of thymine and can be incorporated into DNA in place of thymine. In its normal state 5Bu acts like thymine and pairs with adenine (see COMPLEMENTARY PAIRING but the analogue sometimes undergoes a chemical change called a tautomeric shift and now pairs with guanine. At the next DNA replication an incorrect base will be incorporated into the DNA, causing a TRANSITION SUBSTITUTION mutation (adenine - guanine).