The main function of a gene is to make one/ more proteins. The changes occurring in the sequence of nitrogen bases is called gene mutation. It is also called point mutation. It is of following types:
(i) Deletion: It is a gene mutation caused by the loss of one or more nucleotides from a gene.
(ii) Insertion: It is a gene mutation caused by addition of one or more nucleotides to a gene.
(iii) Inversion:Here segment of DNA is removed and is replaced in an opposite direction.
(iv) Substitution: It is a gene mutation where one nucleotide (A) is replaced by another nucleotide(C).
With the change of a single nitrogen base from the gene, amino acid sequence in protein molecules changes. Thus the structure of a protein is changed. Ultimately this changes the morphology of the organism.