Which Of The Conditions Would Result In The Greatest Amount Of Transcription Of The Lac Operon?

Is mutant lac operon?

Single mutants of the lac operon Such mutant are called constitutive mutants.

Another type of mutant of lacI called Is prevents the repressor polypeptide from binding lactose, and thus will bind to the operator and be non-inducible..

This mutant constitutively represses the lac operon whether lactose is present or not..

Under which conditions are the Lac structural genes expressed most efficiently?

Under which conditions are the lac structural genes expressed most efficiently? When glucose is absent and lactose levels are high, the lac structural genes are expressed the most efficiently. Without glucose, cAMP is produced and CAP can stimulate transcription of the structural genes.

Why is the lac operon negative?

Explanation: The lac operon exhibits both systems. It is a negative control system because expression is typically blocked by an active repressor (the lac repressor) that turns off transcription. The lac repressor binds to the operator region and negatively controls (prevents) transcription.

What is the difference between positive and negative control what is the difference between inducible and repressible operons?

Positive transcriptional control requires an activator protein to stimulate transcription at the operon. In negative control, a repressor protein inhibits or turns off transcription at the operon. What is the difference between inducible and repressible operons? An inducible operon normally is not transcribed.

Under which of the following conditions would a lac operon produce the greatest amount of β galactosidase the least explain your reasoning?

A lac operon would produce the greatest amount of B-galactosidase in condition 1 and the least amount in condition 2 because in the absence of lactose, the repressor binds to the lac operator site and inhibits transcription, and high levels of glucose decreases transcription since RNA polymerase can’t bind as well to …

What is the lac operon an example of?

The lac operon is a classic example an inducible operon. When lactose is present in the cell, it is converted to allolactose. Allolactose acts as an inducer, binding to the repressor and preventing the repressor from binding to the operator. This allows transcription of the structural genes.

What happens when both glucose and lactose are absent?

If both glucose and lactose are both present, lactose binds to the repressor and prevents it from binding to the operator region. … If, however, glucose is absent and lactose becomes the only available carbon source, the picture changes. Lactose still prevents the repressor from binding to the operator region.

When lactose is absent the repressor is active?

Repressors and Activators are proteins that bind to DNA and control transcription. Lactose absent, repressor active, operon off. The lac repressor is innately active, and in the absence of lactose it switches off the operon by binding to the operator.

What does maximal transcription of the lac operon require?

Maximum transcription from the lac operon requires the presence of a cAMP/CRP complex. cAMP/CRP complex binds to a specific sequence in the lac control region called the “CAP” site. … Mutations in the CAP site that prevent cAMP-CRP binding also prevent high levels of expression of the lac operon.

Is lac operon positive or negative?

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.

What turns the lac operon off?

An operon is a group of genes that are regulated together. … When lactose is not present, the DNA-binding protein called ► lac repressor binds to a region called the operator, which switches the lac operon off. When lactose binds to the repressor, it causes the repressor to fall off the operator, turning ► the operon on.

What happens to the lac operon in the absence of lactose?

When lactose is not available, the lac repressor binds tightly to the operator, preventing transcription by RNA polymerase. However, when lactose is present, the lac repressor loses its ability to bind DNA. … When lactose is absent, the lac repressor binds tightly to the operator.

What is lac Z?

The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose. lacY encodes Beta-galactoside permease, a membrane protein which becomes embedded in the cytoplasmic membrane to enable the cellular transport of lactose into the cell.

Why is cAMP low when glucose is high?

When the concentration of intracellular glucose is high (lower panel), cAMP levels are low. Without the adjacent binding of the CAP-cAMP complex, RNA polymerase does not bind to DNA as efficiently, resulting in low rates of transcription for the lacZ, lacY, and lacA genes.

What is the function of LacI in the regulation of the lac operon?

The role of LacI is to inhibit mRNA production for proteins encoded by the lac operon. Transcription is not completely eliminated, but lacZYA mRNA is transcribed only at very low levels.

Which of the conditions would result in the least amount of transcription of the lac operon?

Considering the conditions below, indicate the amount of transcription of the lac operon from least to greatest. If glucose is high, catabolite repression is working and there is the lowest amount of expression of the operon.

How does glucose regulate the lac operon?

Catabolite control of the lac operon. The operon is inducible by lactose to the maximal levels when cAMP and CAP form a complex. … Glucose control is accomplished because a glucose breakdown product inhibits formation of the CAP-cAMP complex required for RNA polymerase to attach at the lac promoter site.