An operon is a region of DNA that consists of a single gene regulated by more than one promoter.
An operon is a region of RNA that consists of the coding regions of more than one gene.
An operon is a region of DNA that codes for a series of functionally related genes under the control of the same promoter.
An operon is a region of DNA that codes for sugar-metabolizing enzymes.
This arrangement of genes is common in bacteria. For example, genes involved in lactose metabolism are clustered in the lac operon of E. coli, and genes involved in tryptophan metabolism are in the trp operon.
RNA polymerase is the enzyme that binds to promoters and transcribes the coding regions of genes into RNA.
In allosteric regulation, genes are expressed constitutively.
In allosteric regulation, a gene is turned off by a repressor protein.
In allosteric regulation, a small molecule binds to a large protein and causes it to change its shape and activity.
In allosteric regulation, a gene is turned on by an activator protein.
Allosteric regulation is an important mechanism for changing enzyme activity, as well as for changing the function of some gene repressors and activators
There is no change—the lacI gene is constitutively expressed.
The lacI gene turns off.
The lacI gene increases its rate of transcription.
The lacI gene turns on.
The lacI gene is expressed regardless of the presence of lactose. Only the structural genes of the lac operon are affected by the presence or absence of lactose.
The lacZ gene encodes b-galactosidase, a key enzyme in lactose metabolism. When lactose is present in the cell, the cell expresses lacZ and metabolizes lactose.
Adenylyl cyclase converts ATP to cAMP, which helps CAP bind and facilitates binding of RNA polymerase to the lac promoter.
The process by which lactose binds to the lac repressor and inactivates it by causing it to change shape is known as allosteric regulation. However, the process by which glucose causes cAMP levels in the cell to drop, thereby preventing CAP from stimulating expression of the lac structural genes, is known as catabolite repression.
A mutation in the lac-Z gene
A mutation in the lac-Y gene
A mutation in the operator sequence
A super repressor mutation
Such a mutation could prevent binding of the repressor, allowing expression under all conditions.
It prevents other sugars from being metabolized until all available lactose has been used.
It ensures that a cell produces enzymes involved in lactose metabolism in a constitutive manner.
It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment.
It ensures that bacterial cells produce lactose only when no other food sources are available.
The cell expends energy to produce the proteins necessary for lactose metabolism only when lactose is present.
When the repressor binds to the operator, RNA polymerase cannot transcribe the structural genes.