BIOL240 Lecture Notes - Lecture 27: Stem-Loop, Tryptophan, Ribosome
15 Mar 2019
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Document Summary
Promoters of positively controlled operons require activator proteins because these promoters have nucleotide sequences that bind to rna polymerase weakly. Negative control: effector molecules can also inhibit transcription by binding to the repressor protein and enhancing its ability to bind to the operator (common for anabolic operons) Attenuation has elements of transcription and translation. Interruption of transcription after initiation but before termination. Attenuation happens right in the middle of the transcription process. If there"s to much of the end product around like tryptophan, then the transcription stops half way. Transcription in bacteria: rho dependent rho protein follows rna pol and removes it from the dna when it reaches a termination sequence, rho independent, rna hairpin loop forms, causing rna pol to dissociate from the dna. When it comes to the terminator region which has weak bonds, it dissociates. Ribosome binds to mrna immediately and starts synthesizing the protein: pol.
