Question:
A---enzyme A------>B----enzyme 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:
B) nutrient B only
Explanation:
The mutant has a mutation in the gene that codes for the enzyme A. Therefore, this mutant would not be able to convert the substance A into B. Without the presence of substance B, the final product can not be formed. However, if the mutant is supplemented with the substrate "B", it can convert the B into the final product (substance C). Therefore, the mutant would be able to grow in the medium to which the already prepared substance B has been added.
