Application Questions And Problems

*17. For each of the following types of transcriptional control, indicate whether the protein produced by the regulator gene will be synthesized initially as an active repressor, inactive repressor, active activator, or inactive activator.

(a) Negative control in a repressible operon

(b) Positive control in a repressible operon

(c) Negative control in an inducible operon

(d) Positive control in an inducible operon

*18. A mutation occurs at the operator site that prevents the regulator protein from binding. What effect will this mutation have in the following types of operons?

(a) Regulator protein is a repressor in a repressible operon.

(b) Regulator protein is a repressor in an inducible operon. 19. The blob operon produces enzymes that convert compound

A into compound B. The operon is controlled by a regulatory gene S. Normally the enzymes are synthesized only in the absence of compound B. If gene S is mutated, the enzymes are synthesized in the presence and in the absence of compound B. Does gene S produce a repressor or an activator? Is this operon inducible or repressible?

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