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(Solved): The trp operon and separate regulatory gene, trpR, are diagrammed below. The trpE, trpD, trpCi trpB ...
The trp operon and separate regulatory gene, trpR, are diagrammed below. The trpE, trpD, trpCi trpB, and trpA genes encode the enzymes required for synthesis of tryptophan. Regions \( L \) and \( A \) are part of the \( 5^{\prime} \) UTR that precedes trpE. a. Expression of the trpE-A genes is under negative control and there are two different mechanisms for preventing their transcription - repression of initiation and attenuation. Describe each mechanism. Include the specific regulatory components that are involved in each mechanism. Also describe the role of tryptophan in each mechanism and what tryptophan interacts with. \( (8 \mathrm{pts}) \) b. If the trpA-E genes cannot be transcribed or any one of these five genes does not encode a functional enzyme, the bacterial cell will not be able to make the amino acid tryptophan. For each of the following mutant strains, predict whether the strain will synthesize tryptophan: 1 = never, 2 = only when tryptophan is low or absent, or 3 = always. \( (6 \) pts) A minus \( (-) \) symbol indicates that the gene or regulatory region is nonfunctional; D indicates that the gene or region is completely deleted. Strain 1: \( \operatorname{tr} p R-\operatorname{tr} p P^{+} \operatorname{tr} p O^{+} \operatorname{tr} p L A^{D} \operatorname{tr} p E^{+} \operatorname{tr} p D^{+} \operatorname{tr} p C^{+} \operatorname{tr} p B^{+} \operatorname{tr} p A^{+} \) \( \operatorname{train} \) 2: \( \operatorname{tr} p R^{+} \operatorname{tr} p P^{+} \operatorname{tr} p O^{+} \operatorname{tr} p L A^{D} \operatorname{trpE^{+}} \operatorname{tr} p D^{+} \operatorname{tr} p C^{+} \operatorname{tr} p B^{+} \operatorname{tr} p A^{+} \) train 3: \( \operatorname{tr} p R^{+} \operatorname{tr} p P^{+} \operatorname{tr} p O^{+} \operatorname{tr} p L A^{+} \operatorname{trp} E^{+} \operatorname{tr} p D^{+} \operatorname{tr} p C^{+} \operatorname{tr} p B-\operatorname{tr} p A^{+} \)