No lactose in the cell The repressor binds to operator, blocking transcription. lacY (permease) lacA lacZ (B-galactosidase) (transacetylase) DNA Terminator RNA polymerase bound to promoter to operator Repressor bound Lactose present in the cell Some lactose is converted to allolactose. This binds to the repressor and alters its shape, so that it can no longer bind to the operator. If glucose is not available, the operon will be transcribed. Transcription Transcription O FIGURE 7.23 Lactose and the lac Operon B-Galactosidease is the enzyme that hydrolyzes lactose into its monosaccharide components. Allolactose Non-functional repressor Permease is the transporter that brings Translation lactose into the cell. The function of transacetylase in lactose catabolism is not fully understood. ? When would the lac operon in E. coli be repressed, and why?

Q: If an abnormal repressor protein could still bind allolactose but the binding of allolactose did not…

A: Operon acts as a single regulated unit having one or more structural genes, promoter gene, a…

Q: How does catabolite repression  work on  gal operon?How could you decide if one particular operon is…

A: catabolite repression : Catabolite repression is a regulatory system by which any microorganism…

Q: Explain how the lac operon is both positively and negativelycontrolled.

A: The lac operon of E. coli contains genes involved in lactose metabolism. It is expressed only when…

Q: Attardi et al. (1963) found that lactose operon mRNA synthesis in coli increased with the addition…

A: Both structural and regulatory genes are found in genomic DNA, and both encode products that act as…

Q: Is proA in the lac operon? Only lacI, lacZ, lacY, are in the lac operon, right?

A: Answer : No,  proA is absent in lac operon.        Additional information : ProA is present in the…

Q: Would a mutation that inactivated lac repressor and prevented it from binding to the lac operator…

A: The negative regulation of the lac operon is done by a repressor, which is a product of the lacI…

Q: What are the main elements of the lac operon and their functions?

A: Operon is the the prokaryotic gene regulatory system in which the expression of polycistronic mRNA…

Q: Under what conditions is lac repressor bound to the lac operon?

A: Lactose operon (Lac operon) was discovered in Escherichia coli. This is studied to understand the…

Q: How does repression work in the lac operon?

A: Lac operon consists of a promoter, operator group of structural genes such as lac A, lac Z, and lac…

Q: Explain how the lac operon exerts positive regulation.

A: operons are gene regulatory elements found in prokaryotes . these are set of genes which are…

Q: What turns the operon on when lactose is present?

A: An operon is defined as a functioning unit of DNA that contains a cluster or group of genes under…

Q: Explain how the lac operon normally functions

A: Lac operon is a group of genes with a single promotor (gets transcribed as single mRNA). These genes…

Q: How can the bacteriophage T7 promoter be used to controlexpression of a eukaryotic gene in…

A: Expression vectors are designed to control the expression of particular cloned genes. The native…

Q: What do you mean by coordinate expression of genes in operon?

A: Answer- In prokaryotes genes are controlled by one promoter region that is called polycistronic…

Q: Draw the structure of lac operon?

A: The operon is a unit of DNA (deoxyribonucleic acid) in which multiple genes that function in the…

Q: If the two trp codons in the leader sequence were mutated to stop codons, what effect would it have…

A: DNA is the preferred carrier of genetic information in most living organisms except for certain RA…

Q: Compare and contrast the functional mechanism of the Inducible - Lac operon  with the Repressible -…

A: Gene expression is a process in which the genetic instructions of genes are utilized to manage…

Q: What was the eventual hypothesis proposed bythe researchers to explain the function of the lacI gene…

A: To define the function of the lacI gene and the regulation of the lac operon.

Q: Why is the TRP operon considered a repressible operon, while the LAC operon is considered an…

A: Operons are areas of DNA which are composed of cluster of related genes which are controlled by…

Q: How is glucose involved in positive control of the lac operon?

A: A set of genes present in E.coli. that regulates the uptake of lactose from the surrounding…

Q: Do you expect operons to occur extensively in Eukaryotes? Yes or no and explain.

A: Operons (clusters of co-regulated genes with related functions) are a well-known feature of…

Q: How does the lac operon help E. coli conserve energy and other resources?

A: Escherichia coli, also known as E. coli, is a Gram-negative, facultatively anaerobic, rod-shaped,…

Q: Describe the organization of the lac operon.

A: Step 1 Inducible Operon System (Lactose Operon) is a regulated operon system in which the structural…

Q: Explain the structure of Lac operon in bacteria.

A: Lactose is a beta-galactoside that E.coli use for energy and as a carbon source after it is broken…

Q: Describe the feature of lac operon?

A: The operon comprises the genes regulating a metabolic reaction. It is also an operon. It mainly…

Q: what is the lac operon ? what happens in terms of the lac operon when lactose is absent from the…

A: The working segment of DNA that codes for proteins is a gene. An operon is a group of genes that are…

Q: Why it is essential to the positive stimulation of transcription of the lac operon ?

A: Lac operon includes the genes that code for the enzymes involved in lactose catabolism.

Q: What led researchers to conclude that a repressor moleculeregulates the lac operon?

A: Lac operon is regulated by the lac repressor molecule.

Q: What are the example of operon?

A: Operon is a group of genes which controls the synthesis process of protein molecules depending on…

Q: What is the major difference between the mechanism involved inattenuation and riboswitches and the…

A: Attenuation is a mechanism that controls gene expression in a bacterial operon and causes premature…

Q: What is a negative inducible operon?

A: Regulated genes can be switched on/off depending on cell's metabolic needs. Operon It is a group of…

Q: What is a bacterial operon and the two types of it?

A: The bacterial genome consists of thousands of different genes located on one chromosome and these…

Gene Interactions

When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.

Gene Expression

Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.