Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur a. genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes. b. enzymes are made of dna, and affected individuals lack dna polymerase. c. many metabolic enzymes use dna as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with dna. d. certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. e. metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.