Explain how a substitution mutation could cause an enzyme not to work (5)

The mutation changes the order of bases so there is a different triplet code present. This results in a different amino acid being coded for in the polypeptide chain. This means a different protein with a different tertiary structure is made. The enzymes active site will also be different and no longer complimentary to the substrate. Therefore no reaction can make place as the substrate can not fit into the enzymes active site any more.