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Secure https://session.masteringgenetics.com/myct/itemView?assignmentProblemID 5078395 Chapter 1 Problem 16.10 x previous 5of5 return to assignment Problem 16.10 Part A Predict the effect on the inducibility of the lac operon of a mutation that disrupts the function of: The crp gene, which encodes the CAP protein Absence of a functional crp would compromise the positive control exhibited by CAP Presence of a functional crp would compromise the positive control exhibited by CAP Submit My Answers Give Up Correct Part B The CAP-binding site within the promoter. With a CAP binding site there would be a reduction in the inducibility of the lac operon. Without a CAP binding site there would be a reduction in the inducibility of the lac operon Submit My Answers Give Up Continue

Explanation / Answer

Mutations in the crp gene that encodes CAP protein would result in reduction in inducibility of lac operon. This is because CAP protein encoded by crp gene binds to cAMP and this CAP-cAMP complex activates transcription of lac operon (in the presence of lactose and absence of glucose) by binding to specific sites on DNA thereby recruiting RNA polymerase to the transcription site. SO, the correct option is option A, Absence of a functional crp would compromise the positive control exhibited by CAP. Mutations in the CAP-binding site within the promoter or absence of CAP binding site within the promoter will prevent the binding of cAMP-CAP complex to the DNA. As a result RNA polymerase cannot bind to the DNA due to which transcription of lac operon genes is reduced or inhibited. So, the correct option is option B, without a CAP binding site there would be a reduction in the inducibility of lac operon.

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