What is point mutation? Give one example.
Mutation in a single nucleotide base of a DNA segment is called a point mutation. It can introduce a premature stop codon, or a nonsense codon, by addition or deletion of the base, in the transcribed mRNA (nonsense mutation) or changes a codon specifying a different amino acid by substitution of one base (missense mutation). For example, replacement of A by T at the 17th nucleotide of the Hbb gene changes the codon GAG (glutamic acid) to GTG (which encodes valine) and causes sickle cell anaemia.
