AnswersDriveGood guess would be the lac operon is found in the gut flora. Humans have genes to produce enzymes to metabolise lactose (unless they're lactose intolerant). This is different to the lac operon in E. coli as human genes are not organised in operons the same way bacterial genes are.
What is the lac operon?
The lac operon (lactose operon) is an operon required for the transport and metabolism of lactose in Escherichia coli and many other enteric bacteria. The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose.
What is a lac operon concept?
The general term for the product of a regulatory gene is a regulatory protein. The Lac regulatory protein is called a repressor because it keeps RNA polymerase from transcribing the structural genes. Thus the Lac repressor inhibits transcription of the lac operon.
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What does the promoter do?
In genetics, a promoter is a region of DNA that initiates transcription of a particular gene. Promoters are located near the transcription start sites of genes, on the same strand and upstream on the DNA (towards the 5' region of the sense strand).
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What does it mean to be an inducible operon?
The lac operon is a negatively controlled inducible operon, where the inducer molecule is allolactose. In negative repressible operons, transcription of the operon normally takes place. Repressor proteins are produced by a regulator gene, but they are unable to bind to the operator in their normal conformation.
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What does the trp operon do?
The trp operon is present in many bacteria, but was first characterized in Escherichia coli. In the lac operon, allolactose binds to the repressor protein, allowing gene transcription, while in the trp operon, tryptophan binds to the repressor protein effectively blocking gene transcription.
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How is Allolactose made?
Galactosidase does this by bonding to lactose and shifting the position where its underlying sugars bond. Once formed, allolactose functions as a lac inducer, molecules that turn on, or initiate the expression of, the lac genes.
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Who found the lac operon?
The Discovery of the lac Operon. In 1961, Francois Jacob and Jacques Monod proposed the operon model of gene regulation in bacteria. The model was based on their study of the genes in E. coli that code for enzymes that affect the breakdown of lactose. Francois Jacob and Jacques Monod.
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Where does RNA polymerase bind and why?
In order to start a new round of transcription, the core RNA polymerase has to be directed to bind at a promoter, defined as the specific DNA sequence where transcription is initiated. There are specific DNA binding factors that bind to promoters and to RNA polymerase.
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What is the inducer of the lac operon?
The inducer in the lac operon is allolactose. If lactose is present in the medium, then a small amount of it will be converted to allolactose by a few molecules of β-galactosidase that are present in the cell. Allolactose binds to the repressor and decreases the repressor's affinity for the operator site.
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What genes control cell differentiation during development explain how they control this?
Most are controlled individually and have regulatory sequences that are much more complex than those of the lac operon. A series of genes called hox genes control the differentiation of cells and tissues in the embryo. The region of mRNA where RNA polymer binds and starts transcription.
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How might a mutation in the regulatory gene affect the lac operon?
Mutations in structural genes typically affect the function of only that structural gene. Mutations in regulator genes can affect the expression of all structural genes in an operon. lac I is the regulator gene of the lac operon. It makes a monocistronic message, and codes for one protein - the lac repressor protein.
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How is Allolactose formed from lactose?
At the start of induction, lactose is transported by one of the one or two Lac permease molecules which are produced by the lac operon in the absence of any inducer. Lactose (1-4-galactosido-β-d-glucose) itself is not an inducer. They isomerize lactose into allolactose before hydrolyzing it into glucose and galactose.
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Is lactose an inducer?
Concept 7: The lac Inducer: Allolactose. Allolactose is called an inducer because it turns on, or induces the expression of, the lac genes. The presence of lactose (and thus allolactose) determines whether or not the Lac repressor is bound to the operator.
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How does the repressor protein prevent transcription?
A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA. An RNA-binding repressor binds to the mRNA and prevents translation of the mRNA into protein.
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What are transcription factors in biology?
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence.
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What type of organisms are operons found?
Operons are found in prokaryotes (bacteria and archaea), and (in rare cases) in eukaryotes. What type of organism are operons found in? Explain the differences b/w the lac and trp operons. technique used to test cells that cannot perform a certain function.
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What is the lac operon?
The lac operon (lactose operon) is an operon required for the transport and metabolism of lactose in Escherichia coli and many other enteric bacteria. The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose.
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Is the lac operon inducible or repressible?
The lac operon is an example of an inducible system. With repressible systems, the binding of the effector molecule to the repressor greatly increases the affinity of repressor for the operator and the repressor binds and stops transcription.
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How the lac operon is regulated?
The regulatory gene lacI produces an mRNA that produces a Lac repressor protein, which can bind to the operator of the lac operon. The Lac regulatory protein is called a repressor because it keeps RNA polymerase from transcribing the structural genes. Thus the Lac repressor inhibits transcription of the lac operon.
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How does the the lac operon work?
A repressor protein binds the operator (control) region upstream of the operon preventing transcription. When lactose is present outside the cell, it crosses the cell membrane and acts as an inducer of the operon. CAP promotes RNA polymerase transcription of genes leading to an increase of lac operon expression.
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Is the lac operon usually on or off?
The lac operon is considered an inducible operon because it is usually turned off (repressed), but can be turned on in the presence of the inducer allolactose.
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What is the lac operon and why is it important?
The lac operon in E coli is a set of four genes which work together to allow the bacterium to make use of lactose for energy. An Operon is a set of genes which are co-transcribed on a single mRNA, controlled from a common promoter. They are the only 2 genes necessary for lactose usage in the cell.