Base Analogues are compounds that are sufficiently similar to normal nitrogenous bases that they may be incorporated in nucleotides in the place of the normal nitrogenous bases. These base analogues often will undergo tautomeric shifts with greater frequency than the normal bases leading to transitional mutations. These are commonly used for inducing mutations. 2-AP will displace Adenine and miss pair with Cytosine. Some mutagens are not incorporated into the DNA, but alter the existing base.
Base damage can prevent replication under some circumstances.
This must be avoided at all costs by organisms or they will be doomed. Some bacteria have an SOS system that responds to such situations and reduce the fidelity of fidelity of positioning complementary bases opposite the sites with damage. UV radiation induces dimer formation and may stimulate the SOS response. Aflotoxin B1 causes guanine to break off from the deoxyribose sugar thereby creating an apurinic site . Deamination of cytosine yields uracil which will pair with adenine leading to a transition mutation.