When an E -...

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When an  E. coli  cell must make tryptophan for itself, all the enzymes are synthesized at one  time. The switch is a segment of DNA called an  operator. The operator, located between the promoter and the enzyme-coding genes, controls the access  of RNA polymerase to the genes. The operator, the promoter, and the genes they control constitute an  operon. The  trp  operon ( trp  for tryptophan) is one of many operons in the  E. coli  genome. By itself, an operon is turned on. RNA polymerase can bind to the promoter and transcribe the  genes. The operon can be switched off by a protein called the  trp  repressor . The repressor binds to the operator, blocks attachment of RNA polymerase to the promoter,  and prevents transcription of the operon’s genes. Each repressor protein recognizes and binds only to the operator of a particular operon. The 
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This note was uploaded on 01/04/2012 for the course BSC BSC1005 taught by Professor Orlando,rebecca during the Fall '10 term at Broward College.

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When an E -...

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