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Lactose is absent
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The lac operon enables a bacterium to build the proteins needed for lactose metabolism only when?
Lactose is present, otherwise the lac operon is not needed and is shut off.
What turns the lac operon on and off?
The lac operon is turned off and on by repressors.
What is a clue that the lac operon is on?
The lac operon uses a two-part control mechanism to ensure that the cell expends energy producing the enzymes encoded by the lac operon only when necessary. In the presence of lactose, the lac repressor halts production of the enzymes encoded by the lac operon.
A lac repressor turns off the lac genes by binding to?
When the lac repressor binds to the O region, RNA polymerase is prevented from beginning the process of transcription. In effect, the binding of the repressor protein turns the operon "off" by preventing the transcription of its genes. (Prentice Hall Biology Book .....Chapter 12 page 310)
Function of genes in the lac operon?
There are 3 structural genes in in lac operon. . namely Lac Z - codes for beta galactosidase (breaks lactose into galactose and glucose) Lac Y - coding for beta galactoside permease ( pumps lactose into the cell) Lac A - coding for transactylase (function is acetylation of lactose and so tht it can act as a messenger hope its not required for you in detail) and a gene called Lac i - coding for repressor protein (switching off the expression of stuctural genes) refer Genetic for gardner of Molecular biology by weaver if you are dealing in detail . .or the info i have provided is sufficient. . (and confusion or doubts mail me at vegi.chaitanya@gmial.com)
The lac operon enables a bacterium to build the proteins needed for lactose metabolism only when?
Lactose is present, otherwise the lac operon is not needed and is shut off.
What turns the lac operon on and off?
The lac operon is turned off and on by repressors.
Why lac operon the gene expression is switch off?
explain the regulation of gene expression in lac operon.
What turns the lac operon off and off?
Repressors
What is a clue that the lac operon is on?
The lac operon uses a two-part control mechanism to ensure that the cell expends energy producing the enzymes encoded by the lac operon only when necessary. In the presence of lactose, the lac repressor halts production of the enzymes encoded by the lac operon.
A lac repressor turns off the lac genes by binding to?
When the lac repressor binds to the O region, RNA polymerase is prevented from beginning the process of transcription. In effect, the binding of the repressor protein turns the operon "off" by preventing the transcription of its genes. (Prentice Hall Biology Book .....Chapter 12 page 310)
Describe how E. coli uses the negative and positive control of the lac operon to economize on RNA and protein synthesis?
if a regulatory protein in its active state turns off the expression of the operon, the operon is said to be negatively regulated by the regulatory protein. if the regulatory protein in its active state truns on the operon, the operon is positively regulated by the regulatory protein. an operon regulated by a repressor is therefore negatively regulated, because the presence of the active repressor prevents transcription of that operon. in contrast, an operon regulated by an activator is positively regulated, because in its active state the activator protein turns on transcription of the operon under its control. the lac operon of E. coli repressor(lac repressor) is synthesized through the activity of the gene lac I, known as regulator gene. the active form of the lac repressor, is a tetramer that contains four copies of the gene I product. in the absence of the inducer, the repressor binds to the lac operator sequence, preventing RNA polymerase from binding to the promoter and transcribing the structural genes. thus the lac operon is negatively regulated associated with the lac operon, there is another site, 16 base pairs upstream of the promoter, which is used for a positive control of the gene expression. this site is called catabolic activator protein site or cyclic AMP(cAMP) protein site or catabolite gene activator(cga) site, because it is utilized for binding of CAP or cga to stimulate gene expression. CAP can bind to this site only when it is bound with cAMP. by binding to it, the CAP-cAMP complex exerts a positive control over the transcription process. it has an effect exactly opposite to that of repressor binding to an operator. yhe effector molecule cAMP determines the effect of CAP on lac operon transcription. presence of glucose inhibits the formation of cAMP and prevents it to bind to CAP
Function of genes in the lac operon?
There are 3 structural genes in in lac operon. . namely Lac Z - codes for beta galactosidase (breaks lactose into galactose and glucose) Lac Y - coding for beta galactoside permease ( pumps lactose into the cell) Lac A - coding for transactylase (function is acetylation of lactose and so tht it can act as a messenger hope its not required for you in detail) and a gene called Lac i - coding for repressor protein (switching off the expression of stuctural genes) refer Genetic for gardner of Molecular biology by weaver if you are dealing in detail . .or the info i have provided is sufficient. . (and confusion or doubts mail me at vegi.chaitanya@gmial.com)
What acts as an on and off switch in an operon?
which part of an operon acts as the on or off switch?
What are features of the lactose operon?
---|CRP|-------------| O |---| Z | Y | A |---CRP: Binding site for activatorO: Operator, binding site for repressorCoding sequences:Z: b-galactosidaseY: lactose permeaseA: thiogalactoside transacetlyase
The tryptophan operon is a repressible operon that is?
Turned off whenever tryptophan is added to the growth medium
What is the role of lactose in regulating lac operon expression?
When the lac operon controls the expression of proteins in the E.coli cell that can break down lactose into two sugars, glucose and galactose. When lactose is present, it binds to the repressor that typically sits on the lac operon, changing the repressor's conformation such that it can no longer bind to the lac operon. Because of this, RNA polymerase can now transcribe the gene into mRNA, which in turn is translated into the proteins that can break down lactose.
