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Unformatted text preview: e defective operator can no longer bind the repressor Lac I in the absence of lactose.
(e) The repressor Lac I binds irreversibly to the defective operator in the absence of lactose.
Question #61 – 64 (4 x 0.25 points) A bacterium has a functional lac operon. For each statement below specify whether it is true or
false by marking (a) for true and (b) for false.
64. The lacZ, lacY and lacA sequence of genes contains only 1 promoter preceding the lacZ
gene. The sequence is therefore an operon.
The lacZ, lacY, lacA sequence of genes is transcribed through 3 identical promoters into 1
mRNA molecule that is then translated into 3 proteins.
RNA polymerase competes with the repressor, LacI, for binding to the promoter/operator
sequence preceding the operon containing lacZ, lacY, lacA.
lacI is expressed constitutively. Question #65 (1 point) The role of the effector in the proper functioning of the lac operon is to:
(a) Bind to the promoter region and block the binding of RNA Polymerase to the promoter.
(b) Bind to the lacI gene to increase production of LacI.
(c) Bind to LacI and change its structure so that LacI loses the ability to bind to the
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This note was uploaded on 01/21/2014 for the course BIOL 112 taught by Professor Benbasat during the Fall '04 term at The University of British Columbia.
- Fall '04