A mutation is a change in the base sequence of DNA that is harmful or sometimes beneficial to the organism. Typically, mutation occurs spontaneously and is considered a rare but continuous event that occurs at a rate of 10 to 6 base pairs. The presence of a mutagen increases the mutation frequency from 10-3 to 10-6 base pairs. Mutations are inherited and mutated genes pass on to subsequent generations. Types of Mutations (A) Point Mutation: This mutation occurs due to a substitution or change in a single base. The types of this mutation are: (i) Transition: Substitution of purine by purine (A to G or G to A) and of pyrimidine by pyrimidine (T to C or C to T). (ii) Transversion: Substitution of purine by pyrimidine or pyrimidine replaced by Purine (G to C or C to G). The effect of point mutations can be one of the following three types of mutations. (a) Missense: In this mutation, the changed codon specifies a different amino acid. The resulting protein may be more or less active. For example, sickle cell disease (disease caused by a point mutation, i.e. T replaced A in the globin gene) (b) Nonsense: this mutation...