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What is a repressible operon?
A repressible operon is a type of operon in bacteria where gene expression is usually active but can be turned off when a specific corepressor molecule binds to the repressor protein. This binding causes the repressor to bind to the operator region of the operon, blocking transcription and thus shutting down gene expression. An example of a repressible operon is the trp operon in E. coli, which is involved in tryptophan biosynthesis.
What is fuction of operator region in operon?
The operator region in an operon functions as a regulatory switch that controls the transcription of the associated genes. It is a specific DNA sequence where repressor proteins can bind, inhibiting RNA polymerase from initiating transcription. When a repressor is bound to the operator, gene expression is turned off; conversely, when the repressor is absent or inactivated, transcription can proceed, allowing the genes to be expressed. This mechanism is crucial for the efficient regulation of gene expression in prokaryotic cells.
In E. coli the tryprophan switches off the trp operon by?
binding to the trp repressor, causing a conformational change that allows it to bind to the operator region of the trp operon. This blocks RNA polymerase from transcribing the genes, turning off expression of the trp operon.
Can eukaryotic Cells control gene expression by using transcription factors?
Yes, eukaryotic cells can control gene expression using transcription factors. Transcription factors are proteins that regulate the transcription of specific genes by binding to DNA and either promoting or inhibiting gene expression. They play a crucial role in controlling when and where genes are turned on or off in response to various signals and cellular conditions.
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
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)
What causes the lac genes in E. coli to turn off?
A lac repressor turns off the lac genes by binding to the operator.
A lac repressor turns ff the lac genes by binding to?
A lac repressor turns off the lac genes by binding to the operator
What Piece of DNA that serves as an on-off switch for transcription?
The operator
What is a repressible operon?
A repressible operon is a type of operon in bacteria where gene expression is usually active but can be turned off when a specific corepressor molecule binds to the repressor protein. This binding causes the repressor to bind to the operator region of the operon, blocking transcription and thus shutting down gene expression. An example of a repressible operon is the trp operon in E. coli, which is involved in tryptophan biosynthesis.
In E. coli the tryprophan switches off the trp operon by?
binding to the trp repressor, causing a conformational change that allows it to bind to the operator region of the trp operon. This blocks RNA polymerase from transcribing the genes, turning off expression of the trp operon.
How do repressors affect promoters?
a repressor is a protein that binds to DNA, which turns off the genes that code for the digestive enzymes. the promoter, located near the digestive enzyme genes, is a section on DNA that serves as the binding site for the enzyme RNA polymers.
The tryptophan operon is a repressible operon that is?
regulated by the availability of tryptophan. When tryptophan levels are high, tryptophan acts as a corepressor, binding to the repressor protein, which then binds to the operator, preventing gene transcription. This allows bacteria to conserve energy by only producing tryptophan when needed.
Can eukaryotic Cells control gene expression by using transcription factors?
Yes, eukaryotic cells can control gene expression using transcription factors. Transcription factors are proteins that regulate the transcription of specific genes by binding to DNA and either promoting or inhibiting gene expression. They play a crucial role in controlling when and where genes are turned on or off in response to various signals and cellular conditions.
The lac operon is shut off when what is absent?
The lac operon is shut off when lactose is absent. In the absence of lactose, the repressor protein binds to the operator site, preventing transcription of the lac operon genes.
What does it mean for a gene to be turned off or not expressed?
When a gene is turned off or not expressed, it means that the DNA sequence within that gene is not being transcribed into mRNA and translated into protein. This can happen through a variety of mechanisms that regulate gene expression, such as DNA methylation, histone modification, and transcription factor binding.
What is the purpose is the safety lanyard on a personal watercraft?
If the operator falls into the water a lanyard between operator and a switch turns the engine off. If engine continued to run the operator would be stranded, the craft would continue uncontrolled perhaps causing damage to other craft, structures, or people; perhaps even running don the operator.
