A researcher is studying the synthesis of a specific amino acid found in Neurospora. She knows that the pathway begins with a precursor that is converted into the amino acid with two known intermediates (Substance Blue and Substance Green). She
accurately predicts that this amino acid synthesis pathway is catalyzed by three enzymes, (I, II, and III). She subsequently identifies three mutants that she calls Mutant I, Mutant II, and Mutant III. With the information about the mutants below place the enzymes in the order that the enzymes act in this pathway. (Note: the numbers I, II, and III don't necessarily indicate the order in which the enzymes appear.)
Mutant I (only Enzyme I is mutated) is unable to synthesize the amino acid even if she provided the mutant with both Substance Blue and Substance Green.
Mutant II (only Enzyme II is mutated) is able to synthesize the amino acid if she provided the mutant with Substance Blue or Substance Green.
Mutant III (only Enzyme III is mutated) is able to make the amino acid if she provided the mutant with Substance Green, but not if she provided the mutant with only Substance Blue.
A) II, I, III
B) III, II, I
C) III, I, II
D) I, II, III
E) II, III, I
F) More than one codon can specify a given amino acid.
Answer: E
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