Step-by-step explanation:
Mutation - any sudden and hereditary change in the genetic set of an organism, which is not explained by the recombination of pre existing genetic variation. Point mutation - Changes in the nucleotide sequence, which alter the amino acid sequence in the polypeptide chain encoded by the gene, leading to a phenotypic change.
When a purine base is replaced by another purine base (A by G or vice versa) or a pyrimidine base is replaced by another pyrimidine base (T by C or vice versa) it is called a transition. In contrast to the transitions we have the so-called transversions, which are mutations where a purine base is replaced by another pyrimidine, or vice versa, that is, a pair C-G is replaced by another A-T or vice versa. It may be a simple substitution of a base pair, which may be by deletion or addition of one or a few bases. Deletion: is the loss of a portion of the chromosome, resulting in the lack of one or more genes