Mutant A: Lacl has a mutation in its DNA binding site such that it cannot bind t
ID: 90065 • Letter: M
Question
Mutant A: Lacl has a mutation in its DNA binding site such that it cannot bind the operator Mutant B: Mutation affects the protein that produces CAMP such that CAMP is produced at a high level all the time. Indicate the expression levels of beta-galactosidase in Mutant A and Mutant B Indicate with +, ++, or - only. +: Expression occurs (low level) ++: Expression occurs (high level) -: No expression almost no expression FYI: Wild type cells in the case of "neither glucose nor lactose" still produce a small amount of beta- galactosidase because Lacl is not always bound to the operator. Although Lacl stays bound to the operator most of the time, sometimes it falls off and allows transcription to take place for a short amount of time.Explanation / Answer
Answer:-
Introduction: -
The lac operon (lactose operon) is an operon required for the transport and metabolism of lactose in Escherichia coli and many otherenteric bacteria.
**Though glucose is the preferred carbon source for most bacteria, thelac operon allows for the effective digestion of lactose when glucose is not available.
Lac I:-
the lacI gene (regulatory gene for lac operon) produces a protein that blocks RNA polymerase from binding to the promoter of the operon.
**This protein can only be removed when allolactose binds to it, and inactivates it.
** The protein that is formed by the lacI gene is known as the lac repressor.
**The type of regulation that the lac operon undergoes is referred to as negative inducible, meaning that the gene is turned off by the regulatory factor (lac repressor) unless some molecule (lactose) is added.
**beta galactosidase production under various conditions:-
Mutant A organism-++,++,++,++ irrespective of glucose presence or absence and lactose presence or absence or both present or absent beta galactosidase production continues due to inability of repressor to bind to DNA because of mutation.
** Mutant -B:-high cAMP thus high CAP..
In presence of lactose beta galactosidase production will be
High..++. Due to removal of repressor.
**in presence of glucose also as cAMP concentration is high in mutant B, but beta galactosidase production Will be low.+
**in presence of both glucose and lactose beta galactosidase production will be high..++.due to removal of repressor.
**In absence of glucose and lactose also beta galactosidase production will be less due to binding of active repressor +.
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