Gene mutation is a change in the nucleotide sequence of DNA. If this sequence changes, then the codons change and sequence of amino acids in a polypeptide changes.
Frame shift Mutations
The mutation occur most often because one or more nucleotides are either inserted or deleted from DNA. This results in a completely new sequence of codons and a nonfunctional protein.
Point MutationsThese involve a change in a single nucleotide and therefore a change in a specific codon. The occurrence of valine instead of glutamate in the beta chain of hemoglobin results in sickle cell disease. Due to point mutation there is enzyme deficiency and homogentisic acid is not further changed into 4 maleyacetoacetic acid as this leads to alkaptonuria.