To discuss PGx, we must first define two terms:
2. Cytochrome P450 (CYP450)
A polymorphism is a variation in a specific gene (allele) that affects at least 1% of the population. It is essentially a mutation that occurs relatively frequently in the population.
CYP450 refers to a family of enzymes found predominantly in the liver. CYP450 enzymes work on a variety of substrates (in this case, drugs), altering their chemical structures to facilitate excretion in the urine and feces.
There are many known polymorphisms which occur in the protein sequences of CYP450 enzymes.