Problem 16.10

The video is a tutorial on a genetics problem (Problem 16.10) concerning the lac operon and the role of the CAP protein (catabolite activating protein) in its regulation. The instructor diagrams the lac operon, including the promoter with RNA polymerase and CAP binding sites, the operator, and structural genes Z, Y, A. They explain that CAP binds to its site only when glucose levels are low, which leads to high cyclic AMP (cAMP) levels via adenylyl cyclase. cAMP binds to CAP, causing a conformational change that allows CAP to bind to DNA and recruit RNA polymerase, enhancing transcription. The problem asks to predict the effect of a mutation in the CRP gene (which encodes CAP) on inducibility of the lac operon. The instructor argues that even without functional CAP, the operon remains inducible by lactose because lactose inactivates the lacI repressor, allowing RNA polymerase to transcribe at a moderate level. They note that the study guide’s answers are similar but phrase it as ‘compromised’ or ‘reduced’ inducibility. The video concludes that mutations in either CAP or its binding site reduce but do not eliminate inducibility.