3. The mmm operon has the sequences A, B, C, and D, which may represent structur

Question

3. The mmm operon has the sequences A, B, C, and D, which may represent structural genes for the enzymes 1 and 2 or regulatory elements. Mutations in genes A, B, C, and D for the enzymes 1 and 2 or regulatory elements Mutations in genes A, B, C, and D have the effects shown in the following table, where a (+) indicates an enzyme is synthesized and a (-) indicates it is not when the compound Mmm is absent or present Mmm present Enzyme 1 Enzyme 2 Mmm absent MutationMmm in sequence Enzyme 1 Enzyme 2 No mutation Describe the regulation of this operon. What are the roles of the genes A, B, C, and D?

Explanation / Answer

Gene A role is to produce enzyme 1.

Since there is synthesis of enzymes in both presence and absence of mmm, then gene B may be acting as operator.

Gene C role is to produce enzyme 2.

Since there is no synthesis of enzymes in both presence and absence of mmm, then gene D may be acting as a promoter.

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