Question 3 Bacteria with mutations in the lac operon and related genes have been
ID: 163950 • Letter: Q
Question
Question 3
Bacteria with mutations in the lac operon and related genes have been created. In your analysis of one of the mutants, you note that the operon is constantly transcribed and is increased in the absence of glucose. You conclude that the mutation is likely to be in ...
the gene that codes for CAP.
the operator (lacO).
the repressor (lacI).
Two of the above.
All of the above.
A.the gene that codes for CAP.
B.the operator (lacO).
C.the repressor (lacI).
D.Two of the above.
E.All of the above.
Explanation / Answer
Answer is D: The Lac operon constitutively expressed when mutation occor in Operator gene and Lac-I gene. So both B & C gives constitutive expression. So answer is D. Lac-I gene encodes a tetrameric Repressor that binds to Operator and stops the transcription of Lac operon genes. Mutation in Lac-I gene cannot produce reperssor which leads to constitutive expression. Similar condition observed in mutation of Operator gene. Mutaion of Operator gene, not promote the binding of repressor and promotes constitutive expression
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