a. Analyze the DNA of the Phenylalanine hydroxylase (PAH) gene in a patient with phenylketonuria revealed a mutation in the protein coding region whose predicted effect would be to replace the amino acid aspartic acid, with histidine. Nevertheless, no mutant protein could be found in the patient’s cells. Briefly explain how this could happen.

b. How is it possible for a gene with a mutation in the coding region to encode a polypeptide with the same amino acid sequence as the non?mutant gene?