(5-BU) An analogue of the naturally occurring pyrimidine thymine (5-methyl uracil), in which bromine replaces the methyl group on carbon five of the pyrimidine ring. During chromosome replication the analogue may be incorporated into DNA in place of thymine, but it is less specific in its pairing properties. Over a series of replications a T:A nucleotide pair could thus eventually be replaced by a C:G pair resulting in a point mutation (see diagram(The figure shows how 5-bromouracil may be incorporated in place of thymine and by mispairing result in an A:T to G:C mutation.)). The ability of 5-bromouracil to produce point mutations without significant chromosomal damage has made it a useful tool in genetic research. Other base analogues with similar effects include 2-aminopurine and 2,6-diami-nopurine, which are analogues of adenine, and 5-bromodeoxycytidine, which is an analogue of cytosine.  |
