Attenuation of trp operon transcription is controlled by...

Question

Attenuation of trp operon transcription is controlled by the formation of stem-loop structures in mRNA. The attenuation function can be disrupted by mutations that alter the sequence of repeat DNA regions 1 to 4 and prevent the formation of mRNA stem loops. Describe the likely effects on attenuation of each of the following mutations under the conditions specified.

Mutated Region Tryptophan Level
a. Region 1 Low
b. Region 1 High
c. Region 2 Low
d. Region 2 High
e. Region 3 Low
f. Region 3 High
g. Region 4 Low
h. Region 4 High

Accepted Answer

Hi, everybody. Let's go on to our next question. How does the 34 stem loop configuration influence the trip operon transcription choice A? It causes the formation of the anti terminator sequence. Choice B it binds to the operator sequence. Choice C it dissociates R N A polymerase from the template DNA strand or choice D it has no effect on transcription. Well, first, let's recall what that 34 stem loop configuration does in the trip opera. It's part of the attenuated system and the 34 stem loop is the terminator structure. It occurs when there's plenty of trip to fan around. So the R N A or excuse me, the ribosome does not have to pause in translating the liter peptide because it can get the two trip to fan residues. It needs, it continues on it blocks region two and so therefore, regions three and four of the M R N A form the stem loop which is a terminator structure. So we can go ahead and eliminate choice A, it causes the formation of the anti terminator sequence because the anti terminator sequence is the 23 stem loop that forms when the ribosome stalls. Choice A is not correct. Choice B it binds to the operator sequence. This is not correct. The 34 stem loop is regions three and four of the M R N A binding to themselves. They don't bind the promoter region or excuse me, they don't bind to the operator sequence. That would be what a repressor protein does. And part of another type of system of regulating the trip, the trip operon, not this attenuated system. Choy C says it dissociates the R N A polymerase from the template DNA strand. Well, this is correct because this is how it terminates transcription. And then choice D says it has no effect on transcription, but this is obviously incorrect because it stops transcription. So that's a pretty significant effect. So choice D is not correct. So again, how does this, how does the 34 stem loop configuration influence the trip operon transcription? Choice C if the associates are any polymer, then the template DNA strand. See you in the next video.

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