The mmm operon, which has sequences A. B, C. and D. encodes enzymes 1 and 2. Mut

Question

The mmm operon, which has sequences A. B, C. and D. encodes enzymes 1 and 2. Mutations in sequences A. B. C, and D have the following effects. where a plus sign (+) means that the enzymes are synthesized, a minus sign (-) means that the enzymes are not synthesized, and a pound (#) means that the enzymes are synthesized but are not functional. mmm absent Enzyme 1 Enzyme 2 mmm present Enzyme 1Enzyme 2 Wild-type + + -Mutation in A # + Mutation in B + + + + Mutation in C + # -Mutation in D - (a) Is the mmm operon inducible or repressible? Explain your answer. (3 points) (b) Indicate which sequence (A, B, C, or D) is part of the following components of the operon and explain your answer. (8 points) Regulator gene: Promoter: Structural gene for enzyme 1: Structural gene for enzyme 2:

Explanation / Answer

a. The operon is repressible. The B gene is a regulator gene. Since it a mutant, it is produced in the absence and presence of mmm. In the wildtype it should not be produced in the absence of mmm.

b. REgulator gene - B

Promoter gene - D

structural gene for enzyme 1 - A

structural gene for enzyme 2 - C

Promoter gene is not related to the absence or presence of mmm. It is only related to the binding of the repressor. Hence, all - signs for the promoter is D.

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