Chapter 14 - Bacterial Gene Regulation Flashcards
The level of gene expression can vary under different conditions
Gene regulation
Genes that are unregulated
Constitutive
What cellular processes are gene regulation important for?
- Metabolism
- Response to environmental stress
- Cell division
Where/when can gene regulation occur?
Any of the points on the pathway to gene expression
Where does gene regulation occur during transcription?
On the gene
What happens when you regulate gene expression during transcription?
Genetic regulatory proteins bind to the DNA and control the rate of transcription
Where does gene regulation occur during translation?
mRNA
What happens when you regulate gene expression during translation?
- Translation repressor proteins can bind to the mRNA and prevent translation from starting
- Antisense RNA can bind to the mRNA and prevent translation from starting
Where does gene regulation occur during post-translation
- Protein
- Functional Protein
What happens when you regulate gene expression during post-translation (in a protein)?
- In feedback inhibition, the product of a metabolic pathway inhibits the first enzyme in the pathway
- Covalent modifications to the structure of a protein can alter its function
Transcriptional regulation involves the actions of what two main types of regulatory proteins?
Repressors and Activators
What binds to DNA and inhibits transcription?
Repressors
What binds to DNA and increases transcription?
Activators
What refers to transcriptional regulation by repressor proteins?
Negative Control
What refers to regulation by activator proteins?
Positive Control
The presence of a small effector molecule may ___ transcription
Increase
What are small effector molecules called?
Inducers
What are genes called that can be regulated with Inducers?
Inducible
In other cases, the presence of a small effector molecule may ___ transcription
Inhibit
What binds to repressors and cause them to bind to DNA?
Corepressors
What bind to activators and prevent them from binding to DNA?
Inhibitors
What type of Inducible Gene?
1. In the absence of the inducer, this repressor protein blocks transcription
2. The presence of the inducer causes conformational change that inhibits the ability of the repressor protein to bind to the DNA
3. Transcription proceeds
Repressor Protein, Inducer Molecule, Inducible Gene
What type of Inducible Gene?
1. This activator protein cannot bind to the DNA unless an inducer is present
2. When the inducer is bound to the activator protein, this enables the activator protein to bind to the DNA and activates transcription
Activator Protein, Inducer Molecule, Inducible Gene
What type of Repressible Gene?
1. In the absence of a corepressor, this repressor protein will not bind to the DNA
2. Therefore, transcription can occur
3. When the corepressor is bound to the repressor protein, this causes a conformational change that allows the protein to bind to the DNA and inhibit transcription
Repressor Protein, Corepressor Molecule, Repressible Gene
What type of Repressible Gene?
1. This activator protein will bind to the DNA without the aid of an effector molecule
2. The presence of an inhibitor causes a conformational change that releases the activator protein from the DNA
3. This inhibits transcription
Activator protein, Inhibitor Molecule, Repressible Gene
What is a regulatory unit consisting of a few structural genes under the controlled by one promoter?
An operon
An operon encodes a ___ that contains the coding sequence for tow or more structural genes
Polycistronic mRNA
What important DNA sequences does an operon contain?
- Promoter
- Terminator
- Structural Genes
- Operator
Who identified the lac operon?
Francois Jacob and Jaques Manod
What are the two parts of the lac operon?
- Regulatory Elements (Promoter, Operator, CAP Site)
- Structural Genes (lacZ, lacY, lacA)
What are the parts of the Regulatory Elements?
Promoter, Operator, CAP site
What are the parts of the Structural Genes?
lacZ, lacY, lacA
What binds RNA polymerase?
Promoter
What binds the lac repressor protein?
Operator
What binds the Catabolite Activator Protein (CAP)?
CAP site
What encodes β-galactosidase and enzymatically cleaves lactose?
lacZ
What encodes lactose permease and requires membrane protein for transport of lactose?
lacY
What encodes galactoside transacetylase and covalently modifies lactose?
lacA
What is unique about lacI?
- It is not considered part of the lac operon?
- It has its own promoter (the lacI promoter)
- Constitutively expressed at fairly low levels
- Encodes the lac repressor
- Only a small amount of protein is needed to repress the lac operon
How can the lac operon be transcriptionally regulated?
- By a repressor protein
- By an activator protein
The binding of which inducer causes conformational change that prevents the lac repressor from binding to the operator site?
Allolactose
What is the activator protein that can transcriptionally regulate the lac operon?
Catabolite Repression
What happens when Catabolite Repression is exposed to both lactose and glucose?
- E. coli uses glucose first, and catabolite repression prevents the use of lactose
- When glucose is depleted, catabolite repression is alleviated, and the lac operon is expressed
What is the sequential use of two sugars by a bacterium?
Diauxic Growth
