Podcast
Questions and Answers
What enzyme is primarily responsible for lactose metabolism in E. coli?
What enzyme is primarily responsible for lactose metabolism in E. coli?
In the absence of an inducer, what happens to the lac operon?
In the absence of an inducer, what happens to the lac operon?
Which structural gene of the lac operon encodes for galactoside permease?
Which structural gene of the lac operon encodes for galactoside permease?
What molecule serves as the inducer for the lac operon?
What molecule serves as the inducer for the lac operon?
Signup and view all the answers
What occurs when glucose is present and lactose is absent in E. coli?
What occurs when glucose is present and lactose is absent in E. coli?
Signup and view all the answers
What binds to the repressor to inactivate it, allowing transcription of the lac operon?
What binds to the repressor to inactivate it, allowing transcription of the lac operon?
Signup and view all the answers
Which three structural genes are part of the lac operon?
Which three structural genes are part of the lac operon?
Signup and view all the answers
What is the purpose of galactoside permease in lactose metabolism?
What is the purpose of galactoside permease in lactose metabolism?
Signup and view all the answers
What happens to the lac operon when lactose levels are high?
What happens to the lac operon when lactose levels are high?
Signup and view all the answers
What is the role of cAMP when glucose levels are low?
What is the role of cAMP when glucose levels are low?
Signup and view all the answers
At which position does the cAMP receptor protein (CRP) bind on the lac promoter?
At which position does the cAMP receptor protein (CRP) bind on the lac promoter?
Signup and view all the answers
Which enzyme is responsible for converting ATP to cAMP in E. coli?
Which enzyme is responsible for converting ATP to cAMP in E. coli?
Signup and view all the answers
What is catabolite repression?
What is catabolite repression?
Signup and view all the answers
What occurs when glucose levels are high in the E. coli cell?
What occurs when glucose levels are high in the E. coli cell?
Signup and view all the answers
Which of the following is a function of the sigma ($\sigma$) subunit in E. Coli RNA Polymerase?
Which of the following is a function of the sigma ($\sigma$) subunit in E. Coli RNA Polymerase?
Signup and view all the answers
Constitutive genes are continuously expressed in most cells because they:
Constitutive genes are continuously expressed in most cells because they:
Signup and view all the answers
Which regions do most bacterial promoters include for interaction with the sigma ($\sigma$) factor of RNA polymerase?
Which regions do most bacterial promoters include for interaction with the sigma ($\sigma$) factor of RNA polymerase?
Signup and view all the answers
Which of the following alterations can impede access of RNA Polymerase to its promoter?
Which of the following alterations can impede access of RNA Polymerase to its promoter?
Signup and view all the answers
Which statement correctly describes inducible genes?
Which statement correctly describes inducible genes?
Signup and view all the answers
What is the main role of the $eta$ subunit in E. Coli RNA Polymerase?
What is the main role of the $eta$ subunit in E. Coli RNA Polymerase?
Signup and view all the answers
Which is an example of a constitutive gene product?
Which is an example of a constitutive gene product?
Signup and view all the answers
Which mechanism allows for coordinated expression of different sets of genes in bacteria?
Which mechanism allows for coordinated expression of different sets of genes in bacteria?
Signup and view all the answers
What is required to turn on the expression of structural genes in positive control mechanisms?
What is required to turn on the expression of structural genes in positive control mechanisms?
Signup and view all the answers
In negative control mechanisms, what is the role of the product from the regulator gene?
In negative control mechanisms, what is the role of the product from the regulator gene?
Signup and view all the answers
Where does a repressor bind to inhibit transcription in negative regulation?
Where does a repressor bind to inhibit transcription in negative regulation?
Signup and view all the answers
In positive regulation, what molecular event facilitates the binding of RNA polymerase?
In positive regulation, what molecular event facilitates the binding of RNA polymerase?
Signup and view all the answers
What triggers the dissociation of the repressor from the DNA in negative regulation I?
What triggers the dissociation of the repressor from the DNA in negative regulation I?
Signup and view all the answers
Which region of the operon does the sigma factor bind to initiate transcription?
Which region of the operon does the sigma factor bind to initiate transcription?
Signup and view all the answers
What is the function of the repressor protein in the operon model?
What is the function of the repressor protein in the operon model?
Signup and view all the answers
What describes an operon?
What describes an operon?
Signup and view all the answers
Study Notes
Gene Regulation
- Cells can change the expression of genes, as seen in the nucleus of an adult skin cell being transferred to an enucleated egg, resulting in an entire tadpole.
Constitutive Genes
- Constitutive genes are essential components of almost all living cells, performing "housekeeping" functions, such as molecules involved in protein synthesis (rRNA, tRNA, RNA polymerase subunits, etc.).
- These genes are continuously expressed in most cells.
E. Coli RNA Polymerase
- The core enzyme consists of α, ββ'ω subunits, while the holoenzyme consists of α2ββ'ωσ subunits.
- Functions of the subunits include:
- α: assembly of the tetrameric core
- β: ribonucleoside triphosphate binding site
- β': DNA template binding region
- σ: initiation of transcription
- Regulation at transcription initiation involves altering the specificity of RNA Polymerase-promoter interaction, impeding access of RNA Polymerase to its promoter, or using activators to enhance polymerase-promoter activity.
Inducible and Repressible Genes
- Inducible genes are expressed when needed, while repressible genes are turned off when not needed.
- Examples include the synthesis of alcohol dehydrogenase, which is only expressed when ethanol is present.
DNA Sequences Involved in Regulation of Gene Expression
- Most bacterial promoters include the conserved -10 region (Pribnow box) and -35 region, which interact with the σ factor of RNA polymerase.
- Some promoters also include the upstream element, which interacts with the α subunit of RNA polymerase.
Mechanisms to Regulate Transcription in Bacteria
- Two main mechanisms to regulate transcription in bacteria are:
- Using different σ factors in RNA Polymerase, such as sigma70 and sigma32, which recognize different classes of promoters and allow for coordinated expression of different sets of genes.
- Binding other proteins, transcription factors, to promoters, which recognize promoters of specific genes, bind small signaling molecules, undergo post-translational modifications, and alter their affinity toward DNA.
Negative Regulation
- In negative regulation, a bound repressor inhibits transcription by binding to the operator region of DNA, preventing RNA polymerase from binding to the promoter region.
- The repressor protein can be released from the operator by a molecular signal, allowing transcription to occur.
Positive Regulation
- In positive regulation, a bound activator facilitates transcription by binding to the promoter region of DNA, enhancing the binding of RNA polymerase to the promoter.
- The activator protein can be released from the promoter by a molecular signal, preventing transcription.
The Lac Operon
- The lac operon is a classic example of gene regulation, consisting of three linked structural genes (lacz, lacy, and lacA) that are transcribed as a unit.
- The lac operon has a promoter, operator, and activator binding site, and is regulated by the lac repressor and CRP (catabolite activator protein).
Induction of the Lac Operon
- The lac operon is induced when lactose is present and glucose is absent, allowing the cell to utilize lactose as an energy source.
- The inducer allolactose binds to the repressor, causing it to release from the operator, and allowing transcription of the structural genes to occur.
The Operon Model
- The operon model is a classic model of gene regulation, consisting of a cluster of related genes that are turned off or on together.
- It includes binding sites for activators and repressors, a promoter, and one or more genes whose expression is controlled by the operon.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the basics of gene regulation, including constitutive genes and their housekeeping functions, as well as the structure of E. Coli RNA Polymerase. Learn about how cells control gene expression.
