Tryptophan Operon and Attenuation quiz #1 Flashcards
Tryptophan Operon and Attenuation quiz #1
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Which of the following pieces of evidence best supports the claim that tryptophan functions as a corepressor in the regulation of the trp operon?
Evidence that tryptophan binds to the trp repressor protein, enabling the repressor to attach to the operator and inhibit transcription of the trp operon genes, best supports the claim that tryptophan functions as a corepressor. How does the regulation of the trp operon differ from the lac operon in response to their respective molecules?
In the trp operon, tryptophan binding to the repressor inhibits transcription, while in the lac operon, lactose binding to the repressor allows transcription to proceed. What is the role of the leader sequence in the trp operon?
The leader sequence contains regions that can fold into secondary structures, influencing whether transcription is terminated or continues based on tryptophan levels. Which regions of the leader sequence form the terminator structure that halts transcription in the trp operon?
Regions 3 and 4 of the leader sequence form a loop that acts as the terminator structure, stopping transcription. What happens to ribosome movement and transcription when tryptophan levels are low in the cell?
Ribosomes stall at tryptophan codons due to scarce tryptophan tRNA, promoting the formation of the anti-terminator structure and allowing transcription to continue. Why does attenuation allow transcription to continue when translation stalls at the leader sequence?
Stalling at tryptophan codons enables regions 2 and 3 to pair, forming the anti-terminator structure that permits transcription to proceed. How does the TRAP protein regulate the trp operon in some prokaryotes?
When tryptophan is abundant, TRAP binds to tryptophan and the leader sequence, forming a terminator structure that stops transcription. What is the function of the anti-TRAP protein in trp operon regulation?
Anti-TRAP binds to TRAP when tryptophan is low, promoting the anti-terminator structure and allowing transcription to continue. Why can prokaryotic cells regulate the trp operon in multiple ways?
Prokaryotic cells have evolved various independent mechanisms, such as repressors, attenuation, and TRAP/anti-TRAP systems, to regulate the trp operon due to their long evolutionary history. How does the presence of a stop codon in the leader sequence affect attenuation in the trp operon?
When translation does not stall and reaches the stop codon, it facilitates the formation of the terminator loop between regions 3 and 4, halting transcription.
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