Which type of mutation may lead to the sickle cell anemia?

A substitution is a mutation that exchanges one base for another that is a change in a single chemical letter such as switching an A to a G. Such a substitution could change a codon to one that encodes a different amino acid and cause a small change in the protein produced. For example sickle cell anemia is caused by a substitution in the beta-haemoglobin gene which alters a single amino acid in the protein produced. Sickle cell anemia is a disease in which your body produces abnormally shaped red blood cells. The cells are shaped like a crescent or sickle. They do not last as long as normal round red blood cells which lead to anemia.