OBJECTIVE LIFE SCIENCE
MOLECULAR BIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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glucose sensor
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start acting as repressor when glucose is present
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block transcription of operon in certain condition
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bind to isomer of allalactose
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Detailed explanation-1: -The lac repressor acts as a lactose sensor. It normally blocks transcription of the operon, but stops acting as a repressor when lactose is present. The lac repressor senses lactose indirectly, through its isomer allolactose . Catabolite activator protein (CAP) acts as a glucose sensor.
Detailed explanation-2: -In molecular genetics, a repressor is a DNA-or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA.
Detailed explanation-3: -Glucose and the lac Operon coli, so the genes involved in glucose breakdown (catabolism) are expressed constitutively (always transcribed). In the presence of glucose, the lac operon is not needed, so transcription of the lac operon is turned off (catabolite repression).