Phenylketonuria (pku) is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. this amino acid is not otherwise produced by humans. therefore the most efficient and effective treatment is which of the following? a) feed them the substrate that can be metabolized into this amino acid. b) transfuse the patients with blood from unaffected donors. c) regulate the diet of the affected persons to severely limit the uptake of the amino acid. d) feed the patients the missing enzymes in a regular cycle, i. e., twice per week.