er ONE question from Question 1 and 2 ormally in the lac operon, the promo upstr
ID: 259057 • Letter: E
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er ONE question from Question 1 and 2 ormally in the lac operon, the promo upstream of the operato cell to regulate transcription from the lac operon expressed at all)? Briefly explain your answer. (a) a separation between the promoter and the operator of 5 extra nucleotides (b) reversing the order of the promoter and operator so that the operator is upstream of the rono ene (lac) of the lac (c) moving the operator from its normal upstream location to between the 1 gene oter and the operator regions overlap slightly, with the promoter being r region. What would be the effects of the following changes in the DNA on the ability of the according to the level of lactose (i.e., constitutive, inducible, or not (lacZ)and2 gene( op eron - what are the expression pattern for lacZ and for lac?? 2. (a) A number of mutants have been found in the genes of the lac operon. For each of the following partial diploids of E. coli, indicate whether B-galactosidase (lacZ) and galactoside permease inducibly or not expressed at all. Give a brief explanation. (lacY) will by synthesized constitutively, Permease (lac Y) ?-galactosidase (lacZ) (b) Which experiment in question (a) indicated that the promoter is cis-acting? Why?Explanation / Answer
Promoter is the place where rna polymerase binds and operator is the place where inhibitor binds.
A) Addition of extra 5 nucleotides will still have the operon inducible because rna polymerase can still bind to the promoter and lactose can still remove inhibitor from operator and make the operon work.
B) If operator is upstream of promoter than even if the inhibitor is present, it won't be able to inhibit the RNA polymerase activity and the expression will be constitutive
C) If the operator is between lacZ and lac Y then the expression of lacZ will be constitutive because there is no inhibitor present in between the lacZ gene but the expression of lacy will be inducible.
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