In the trp operon, when trp levels are high, the ____________ stem-loop forms, and transcription of...

In the trp operon, when trp levels are high, the ____________ stem-loop forms, and transcription of the structural genes ________________ .

		1-3, continues
		3-4, continues
		2-3, continues
		3-4, ends
		2-3, ends

Expert Solution

Answer - Trp poeron is an anabolic operon by which synthesis of amino acid tryptophan takes place.

The operon consists of regulatory region and structural gene, in regulatory region Trp repressor, promoter, operator and leader region are present. Structural gene consist of 5 genes Trp A TrpB, TrpC, TrpD, TrpE.

Transcription and translation of structural genes is responsible for Trp synthesis, which is regulated by cellular Trp concentration.

Leader frame consists of 4 regions Region 1,2,3,4. which acts as ribiswitches for transcription attenuation.

When Trp level is low the ribosome pauses at Trp codon in sequence 1 and formation of paired structure and prevents attenuation, and transcription goes on

When Trp level is high ribisome quickly translates sequence 1 and blocks sequence 2 from making hair pin loop between region 2 and 3, and a paired structure stem loop between region 3 and 4 is formed which acts as attenuator and terminates transcription.

Hence here option 4 is correct.

In the Trp operon when the Trp levels are high the 3-4 stem loop forms and transcription of structural genes end.

gladiator answered 2 years ago

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