Altering DNA Sequences by Point Mutations - In these type of mutations, a single nucleotide is altered or changed. These mutations are also called as micro lesions, as they are not visible under the microscope. The mutation can be observed only when the wild type and mutant DNA sequence is compared.

Point mutations do not alter the length of the DNA molecule. Point mutations are further classified into two types based upon the type of nucleotide they alter. (i.e., purine or pyrimidine).