Question

Enzyme A Enzyme B
A--------->B----------->C
Refer to the metabolic pathway illustrated above. If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on medium supplemented with _____.
A) nutrient A only
B) nutrient B only
C) nutrient C only
D) nutrients A and C

Answer 1

Answer:

B) Nutrient B only

Explanation:

According to the given information, A, B, and C are required for the normal growth of the organism. The mutant strain has mutated gene A and therefore, can not convert the A into B. However, the given mutation strain is able to convert B into C. If the mutant strain is supplemented with "B", it would be able to form C. In absence of "B" in the medium, the strain would not be able to form both B and C. Therefore, presence of "B" is required in the medium for the given mutant strain.