5. As you know, the lac promoter is a poor intrinsic promoter: it is transcribed efficiently onlywhen CAP-CAMP is bound nearby.Imagine that a culture of E. coli cells is mutagenized and spread on an agar plate containingIPTG, glucose, and X-Gal. Most of the resulting colonies are white but a few are blue.[IPTG is a lactose analog that binds to and inactivates the lac repressor; unlike lactose, IPTGdoes not require Lac Permease (LacY) to enter the cell. X-gal is a substrate of B-galactosidasethat yields a blue product when cleaved by the enzyme; X-gal does not bind to the lacrepressor. For the purpose of this problem, assume that anything less than maximal inductionof B-galactosidase results in a white colony.(i) Why was it expected that most of the colonies would be white?(ii) Describe two different mutations mapping within protein-coding DNA that can account forthe blue colonies. The two mutations should map in different genes and need not map to the lacoperon. Name the gene with the mutation and explain how the mutation alters the function ofthe protein and thereby yields blue colonies.(iii) Describe two different mutations that do NOT map within a protein-coding region thatcan account for the blue colonies. The two mutations should affect distinct aspects of lacregulation.(iv) Predict whether each of your four mutations would be dominant or recessive to wild-type.Explain briefly.(v) Which of the two classes of mutations (i.e. those described in parts ii and iii above) influence"trans-acting" functions and which influence cis-acting functions?

Name: 5. As you know, the lac promoter is a poor intrinsic promoter: it is
Uploaded: 2024-03-20T06:42:41.000Z
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Description: 5. As you know, the lac promoter is a poor intrinsic promoter: it is transcribed efficiently onlywhen CAP-CAMP is bound nearby.Imagine that a culture of E. coli cells is mutagenized and spread on an agar plate containingIPTG, glucose, and X-Gal. Mos