Answer:
The correct answer is option a. "Polymorphisms of genes encoding metabolizing enzymes".
Explanation:
Although doctors prescribe defined doses of drugs according to the patient, an individual can respond differently to a drug according to its specific genomic sequence. The influence of the genome in this case comes from polymorphisms of genes encoding metabolizing enzymes. The study of these polymorphisms is known as Pharmacogenomics, and the most important enzymes that metabolize drugs include: cytochrome P450, cytochrome b5 and NADPH-cytochrome P450.