Question

You are studying a biochemical pathway in the mold Neurospora where enzyme 1 converts the initial substrate into intermediate substrate A; enzyme 2 converts intermediate substrate A into intermediate substrate B; enzyme 3 converts intermediate substrate B into intermediate substrate C; and enzyme 4 converts intermediate substrate C into the end product, an amino acid that is essential for growth. You isolate a mutant that is unable to grow on minimal media. Which data would provide the strongest support for the hypothesis that this mutation occurred in the gene that codes for enzyme 2?

a. The mold can grow on rich medium plus intermediate substrate C, but not on rich medium plus intermediate substrate B.b. The mold can grow on minimal medium plus intermediate substrate B, but not on minimal medium plus the initial substrate.c. The mold can grow on minimal medium plus intermediate substrate B, but not on minimal medium plus intermediate substrate A.d. The mold can grow on rich medium plus intermediate substrate D, but not on rich medium plus intermediate substrate C.e. The mold can grow on minimal medium plus intermediate substrate A, but not on minimal medium plus intermediate substrate C.

Answer 1

The correct answer is option c. "The mold can grow on minimal medium plus intermediate substrate B, but not on minimal medium plus intermediate substrate A".

Step-by-step explanation:

In the study stated in the question, a series of enzymes in the mold Neurospora make it able to growth on minimal medium. If a mutant of Neurospora is not able to growth on minimal medium and the mutated gene is on enzyme 2 it is likely that the mold would grow on minimal medium plus intermediate substrate B, but not on minimal medium plus intermediate substrate A. If enzyme 2 is the only enzyme mutated, the mold would need the intermediate substrate B to remediate the lack of enzyme 2 which is the one that produces it. However, the mold would not be able to growth in a media plus intermediate substrate A because the lack of the enzyme 2 will not allow to convert it to substrate B.