Biology 1002B Lecture Notes - Tryptophan, Permease, Lac Repressor
10 Mar 2013
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Sd box: understood by the cell as rna. Genes that code for subunits of enzymes are together on bacterial chromosome. Single promoter can serve all those genes, together called transcription unit. Transcription gives rise to one long mrna molecule. Key advantage for grouping genes single on and off switch can control the whole cluster of genes coordinate control . Switch is a segment of dna called an operator: positioned within promoter or between promoter & enzyme-coding genes. Operator controls access of rna polymerase to genes. Operon: together operator, promoter and genes they control, entire stretch of rna required. Is usually off but can be stimulated (induced) when a specific small molecule interacts with a regulatory protein: ex. Repressible operon: transcription is usually on but can be inhibited (repressed) when a specific small molecule binds allosterically to a regulatory protein, ex.
