A single base mut

The above statement is correct. It is because if mutation takes place at the third base pair, it does not lead to a phenotypic change. These mutations are known as silent mutations. If the mutations take place at any other base than the third base phenotypic changes may take place. Forexample: Substitution of Valine instead of Glutamic acid in the beta haemoglobin chain of the RBC’S leads to sickle cell anaemia.