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Unformatted text preview: able to bind to trp operon and inhibit initiation of transcription (Fig. 6.11). But transcriptional initiation never totally blocked. Transcriptional attenuation increases stringency of inhibition . Mechanism of transcriptional attenuation : (Fig. 6.12) animation later Requires a specific regulatory sequence called attenuator . It lies somewhere downstream of the transcription start site in the transcribed and translated region of the operon . The attenuator contains a premature termination signal (a GC-rich inverted repeat followed by adenines, sequences 3 and 4 in Figure). If transcription and translation proceed normally (under high tryptophan levels) the mRNA is terminated prematurely and no complete protein can be synthesized....
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- Fall '10