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 lac operon  



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Author5 Posts
  #1

An investigator has isolated a bacterium that, in the absence of glucose, constitutively produces the proteins coded for by the lac operon. Which of the following statements explains this observation?

A)the promoter has a mutation that prevents RNA polymerase from binding

B)there is missense mutation in the gene for beta-galactosidase

C)the gene for the catabolite activator protein is mutated and inactive

D)there is a mutation in the attenuator sequence

E)the gene for the repressor protein is mutated and inactive


please explain your answer, thanx




  #2

E

if no repressor protein --> nothing stopping Lac Operon from expression


  #3

https://www.prep4usmle.com/forum/thread/70314/

somewhat related question, please answer



  #4

E
If proteins are constantly produced in absence of glucose then we can think about 3 possibilities:
1-repressor is absent
2-repressor can't bind to operator
3-operator is defective



  #5

repressor gene part of spesific respone element if inactivaed by mutation,,,so gene encode the protein will be under effect of promoter only(which responsible for normal rate of protein transcription in absense of glucose,,,,,,,,,,,,,,,E,,,,,,,,,,,,,,,,,





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