lacI + lacP + lacO + lacZ - lacY + / lacI - lacP + lacO + lacZ + lacY - Indicate
ID: 42236 • Letter: L
Question
lacI+lacP+lacO+lacZ-lacY+ / lacI-lacP+lacO+lacZ+lacY-
Indicate synthesis of B-galactoside and permease in the presence of absence of lactose.
The answer is no synthesis of B-galactoside and permease when there is no lactose, but there is synthesis of both in the presence of lactose. My question is WHY?
The first strain has a non working lac Z gene and the second strain has a non working lac Y gene.... theyre both cis-acting how is it possible for both genes to be expressed in the presence of lactose?
lacI+lacP+lacO+lacZ-lacY+ / lacI-lacP+lacO+lacZ+lacY-
Explanation / Answer
In the presence of glucose beta galactosidase and permease synthesis increases in the cell. The Cyclic adenosine monophosphate (cAMP) signals the abscence of glucose and allows the binding of CAP (catabolic activator protein) to its binding site. RNA polymerase now binds to the DNA. Thus, in the abscence of glucose ?-galactosidase concentration increases and enables the cell to hydrolyse lactose and release galactose and glucose (CAP binding do not occur in the presence of glucose).
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