Question

You are studying a biochemical pathway and isolate mutants I, II, and III. Mutant I can grow if you supplement the medium with Z. Mutant II can grow if you supplement the medium with X, Y, or Z. Mutant III can grow if you supplement the medium with X and Z, but not if you supplement the medium with Y. What is the order of X, Y, and Z in this biochemical pathway?
a) X, Y, Z
b )Y, Z, X
c) Z, X, Y
d) Y, X, Z
e) X, Z, Y

Answer 1

Answer:

d) Y, X, Z

Explanation:

Mutant I only grows when the medium is supplemented with Z. So Z is the final product of biochemical pathway since supplying other intermediates do not lead to any growth.

Mutant III can grow if medium is supplemented with X and Z but not with Y. This means that Y is the first intermediate in this pathway since mutant III is not able to convert it into X and hence needs to be supplemented with next intermediate product X for growth.

Hence the correct order of X, Y and Z in this biochemical pathway is Y, X, Z.