46 Questions
What function do constitutive gene products perform?
Housekeeping
Which of the following molecules is involved in protein synthesis and is a product of constitutive genes?
rRNA
In what kind of cells are the genes for constitutive gene products continuously expressed?
Most cells
Which of the following is NOT an example of a molecule produced by constitutive genes?
Glucagon
Why are constitutive genes important in cells?
They are essential for basic cellular functions
What is a positive method of regulating transcription initiation?
Use of activators to enhance polymerase-promoter activity
Which method impedes transcription initiation?
Impaired access of RNA Polymerase to its promoter
Alteration in RNA Polymerase-promoter interaction can be:
Positive or negative
What role do activators play in transcription initiation?
Enhance polymerase-promoter activity
Which factor negatively affects RNA Polymerase function?
Impedance of RNA Polymerase access to its promoter
Which process directly follows the transcription of a gene?
Posttranscriptional processing
At which stage is the mRNA translated into a protein?
Translation
What controls the amount of primary RNA transcript made?
Transcription
Modifications made to the primary transcript to become mature mRNA is known as what?
Posttranscriptional Processing
Which process describes the targeting of the protein to its location?
Protein targeting and transport
Which is a control level that affects the intrinsic activity of a protein?
Alteration of the intrinsic activity of the protein
What is the composition of the E. coli RNA Polymerase core enzyme?
α₂ β β' ω
What function does the β subunit of E. coli RNA Polymerase serve?
Ribonucleoside triphosphate binding site
Which subunit of the E. coli RNA Polymerase is NOT part of the core enzyme?
σ
Which function pertains to the σ subunit of E. coli RNA Polymerase?
Initiation of transcription
What is the function of the α subunit in E. coli RNA Polymerase?
Assembly of the tetrameric core
Which component of RNA Polymerase is responsible for recognizing different classes of promoters?
Sigma factor
What role do transcription factors play in bacterial transcription regulation?
They recognize promoters of specific genes and regulate transcription
How can transcription factors alter their affinity toward DNA?
By binding to small signaling molecules and undergoing post-translational modifications
What is the main effect of different sigma factors on gene expression in bacteria?
They allow RNA Polymerase to recognize different sets of promoters
What is the consequence of post-translational modification of transcription factors?
It alters their affinity toward DNA
Where are the skin cells of the adult frog cultured?
In a petri dish
What destroys the nucleus of the unfertilized egg?
UV light
What is injected into the enucleated egg?
A nucleus from the skin cell
What develops after the nucleus is injected into the enucleated egg?
A normal embryo
What is the final stage in the sequence shown in the diagram?
Tadpole
What is the primary condition under which certain gene products are needed for cell growth?
Certain environmental conditions
What controls the synthesis of gene products needed only under certain conditions?
Regulatory mechanisms
What happens when ethanol is consumed concerning alcohol dehydrogenase?
The enzyme production starts in 30 minutes
Which statement correctly describes the role of alcohol dehydrogenase when ethanol is not consumed?
The enzyme is repressed
Which scenario leads to the production of alcohol dehydrogenase?
Drinking ethanol
Which region of bacterial promoters is also known as the Pribnow box?
-10 region
What is the function of the UP element in some bacterial promoters?
It interacts with the α subunit of RNA polymerase.
What sequence is found at the -35 region in bacterial DNA?
TTGACA
What does the σ factor of RNA polymerase interact with?
-10 region
What is the primary role of bacterial promoters?
Initiate mRNA synthesis
Which of the following describes the initial control point for regulating the amount of a protein in the cell?
Amount of primary RNA transcript made
What process is involved in converting pre-mRNA into mature mRNA?
Processing of pre-mRNA
Which level of control affects how much protein is synthesized from mRNA?
Amount of protein made from the mRNA
Which process ensures that proteins reach their correct location within the cell?
Protein targeting and transport
At which point can the intrinsic activity of a protein be altered?
Posttranslational modification
Study Notes
Constitutive Genes
- Essential components of almost all living cells, performing a "housekeeping" function
- Examples: molecules involved in protein synthesis (rRNA, tRNA, RNA polymerase subunits, etc.)
Gene Expression Regulation
- Cells can change the expression of genes
- Example: nucleus of an adult skin cell can be transferred into an enucleated egg to produce a normal tadpole
Regulation at Transcription Initiation
- (+) Alter specificity of RNA Polymerase-promoter interaction
- (-) Impede access of RNA Polymerase to its promoter
- (+) Use of activators to enhance polymerase-promoter activity
Inducible and Repressible Genes
- Gene products needed for cell growth only under certain environmental conditions
- Example: alcohol dehydrogenase (synthesized only in response to ethanol)
Levels of Control of a Protein's Amount and/or Activity
- Amount of primary RNA transcript made
- Processing of pre-mRNA into mRNA
- Rate of degradation of the mRNA
- Amount of protein made from the mRNA
- Alteration of the intrinsic activity of the protein
- Efficiency of targeting of the protein to its location
- Rate of degradation of the protein
E. coli RNA Polymerase
- Core enzyme: α₂ β β΄ω
- Holoenzyme: α₂ β β΄ ωσ
- Functions of subunits:
- α: assembly of the tetrameric core
- β: ribonucleoside triphosphate binding site
- β': DNA template binding region
- σ: initiation of transcription
Mechanisms to Regulate Transcription in Bacteria
- Use of different σ factors in RNA Polymerase
- Binding of transcription factors to promoters
- Recognition of promoters of specific genes
- Binding of small signaling molecules and post-translational modifications
DNA Sequences Involved in Regulation of Gene Expression
- Conserved -10 region (Pribnow box) and -35 region in most bacterial promoters
- Interact with σ factor of RNA polymerase
- Upstream element interacts with α subunit of RNA polymerase
Learn about the essential genes that continuously express housekeeping functions in almost all living cells, including molecules involved in protein synthesis.
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