How is lac operon transcription regulated by the prescence or abscence of lactos
ID: 79939 • Letter: H
Question
How is lac operon transcription regulated by the prescence or abscence of lactose?
A) When lactose is NOT available, the repressor will bind to the promoter and block RNA polymerase from transcribing the genes of the lac operon.
B) When lactose is available, the repressor will bind to the lactose instead of blocking RNA polymerase
C) When Lactose is NOT available , the repressor will bind to allolactose.
D) When lactose is available , allolactose is produced and binds to the operator, blocking RNA polymerase.
E) In the abscence of lactose, transcription occurs at a low level resulting in the production of allolactose which in turn stimulates the cell to take up lactose.
Explanation / Answer
The correct answer are (A) and (B)
In the absence of a lactose the repressor will binds to the operator site which is located near the promoter site. Hence blocks the binding of RNA polymerase to the promoter site hence blocking the expression..!!
In the presence of a lactose the repressor will binds to the allolactose and will undergo a confirmational change in it's structure which results in the release from the operator site hence the RNA polymerase can binds and results it's expression..!!