Phenylketonuria (pku) is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. the 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, such as twice per week. e) feed the patients an excess of the missing product.