Explanation

Mutations are rare events in nature and are then described as spontaneous mutations. Some of these mutations originate from mistakes in normal duplication of DNA. Transitions may be produced by tautomeric shift or ionisation of bases which leads to mistaken A–C base pairing and more frequently mistaken G–T base pairing. Guanine pairs with the rare enol form of thymine and is thus considered as hotspot for spontaneous point mutations.