Bread mold can grow in a minimal medium without supplements (wild type) while certain mutated strains (mutants) can only grow in a minimal medium that is supplemented with specific intermediates found in the following metabolic pathway for arginine synthesis:

minimal ------> ornithine -------> citrulline ------> arginine, where enzyme 1 converts the precursor to ornithine, enzyme 2 converts ornithine to citrulline, and enzyme 3 converts citrulline to arginine.
Which of the following would be TRUE of a strain that can grow in minimal medium containing ornithine, citrulline, or arginine, but not in minimal medium alone?
A. The strain would have a mutation in the gene that encodes enzyme 1.
B. The strain would have a mutation in the gene that encodes enzyme 2.
C. The strain would have a mutation in the gene that encodes enzyme 3.
D. The strain would have a mutation in the gene that encodes for enzymes 1, 2, and 3.
E. The strain would be the wild type with no genetic mutations.


A. The strain would have a mutation in the gene that encodes enzyme 1.

Biology & Microbiology

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