BLOCK 3: MBG: (3.5) RNA AND GENE REGULATION

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Questions and Answers

What role does a co-repressor play in prokaryotic gene regulation?

It forms a complex with a repressor to inhibit gene expression. (correct)

It enhances the transcription process by increasing promoter access.

It activates transcription by promoting RNA polymerase binding.

It helps in the removal of transcription factors from the DNA.

Negative regulation in prokaryotic gene control is primarily about:

Turning off genes that are currently on. (correct)

Enhancing transcription at the promoter.

Activating all genes regardless of need.

Turning on genes that are currently off.

An inducer functions in gene regulation by:

Increasing the levels of general inhibitors around DNA.

Blocking transcription by preventing polymerase binding.

Enabling the activation of transcription at the start site. (correct)

Facilitating the formation of a repressor complex.

Why might a prokaryotic cell choose to regulate gene expression?

To conserve energy and resources when certain substrates are absent. Signup and view all the answers

In the operon model, which sequence is key for gene regulation?

The promoter sequence. Signup and view all the answers

Which small effector molecule prevents gene expression?

Repressor. Signup and view all the answers

What is the primary function of enhancers in gene regulation?

To activate transcription and increase gene expression. Signup and view all the answers

Which of the following best describes the role of transcription factors in gene regulation?

They determine the rate of transcription by binding to DNA. Signup and view all the answers

What is the primary benefit of using an inducer in gene regulation?

To conserve energy by activating genes only when necessary Signup and view all the answers

How do prokaryotic and eukaryotic organisms differ in their gene regulation?

Eukaryotes possess split genes with introns, unlike prokaryotes Signup and view all the answers

What is the primary function of the liver in the context of cellular responses?

To maintain blood glucose levels and manage toxins Signup and view all the answers

Which statement accurately describes eukaryotic gene promoters?

Each gene can have its own promoter, sometimes multiple. Signup and view all the answers

What role do transcription factors play in gene expression?

They enhance or repress the transcription of specific genes. Signup and view all the answers

In terms of environmental sensitivity, how do prokaryotes respond compared to eukaryotes?

Prokaryotes can rapidly adapt to environmental changes. Signup and view all the answers

What are CPD islands associated with in gene expression?

Methylation patterns that regulate gene activity Signup and view all the answers

What is one aspect of the operon model as it relates to gene expression?

It can control a group of genes with a single promoter. Signup and view all the answers

What is the primary role of the transcription factor TF 2d?

To orient and recruit RNA polymerase to the promoter Signup and view all the answers

How do enhancers influence gene expression?

By bending DNA to bring transcription factors close to the promoter Signup and view all the answers

Which statement about enhancers is correct?

Enhancers can interact with promoters from different chromosomes Signup and view all the answers

What ultimately regulates gene transcription most commonly?

At the level of transcription factors and their interactions Signup and view all the answers

What happens if transcription factors cannot be recruited to the promoter?

Gene expression will not occur Signup and view all the answers

Which of the following factors affects the binding affinity of the polymerase to the promoter?

The variable binding affinity of transcription factors Signup and view all the answers

What role do small effector molecules play in gene regulation?

They enhance the recruitment of transcription factors to the promoter Signup and view all the answers

Which component is essential for the formation of the transcriptional complex at the promoter?

General transcription factors like TF 2d with RNA polymerase Signup and view all the answers

What is the main function of the promoter in DNA transcription?

To serve as the binding site for RNA polymerase Signup and view all the answers

Which consensus sequence is commonly found in prokaryotic promoters?

TATAAT Signup and view all the answers

What happens at the termination site during transcription?

The RNA transcript is released Signup and view all the answers

How do eukaryotic promoters primarily differ from prokaryotic promoters?

They are generally longer and more complex. Signup and view all the answers

What is the role of transcription initiation factors in the process of RNA transcription?

They help RNA polymerase bind to the promoter. Signup and view all the answers

What best describes the difference between sense and antisense strands during transcription?

The sense strand contains the coding information for the synthesis of RNA. Signup and view all the answers

Which of the following accurately reflects the significance of promoters in gene transcription?

Promoters facilitate the binding of transcription factors for RNA polymerase recruitment. Signup and view all the answers

What characterizes polycistronic mRNA, particularly in prokaryotic cells?

It encodes multiple proteins from a single mRNA strand. Signup and view all the answers

How do eukaryotic transcription termination processes differ from prokaryotic processes?

Eukaryotic termination involves specific sequences and factors, unlike prokaryotes. Signup and view all the answers

What is the primary role of transcription factors in gene transcription?

They facilitate RNA polymerase binding and initiate transcription. Signup and view all the answers

What type of RNA does RNA Pol I primarily transcribe?

Ribosomal RNA (rRNA) Signup and view all the answers

Which statement about eukaryotic RNA polymerases is correct?

Each polymerase has distinct functions in transcription. Signup and view all the answers

What can happen during the termination of transcription by RNA Pol II?

Transcription can continue beyond the termination sequence. Signup and view all the answers

Which of the following is a function of RNA Pol III?

Transcribes transfer RNA (tRNA) genes. Signup and view all the answers

What role does the TTFI termination factor play in transcription?

It is specifically involved in RNA Pol I termination. Signup and view all the answers

What is the primary structural difference between DNA and RNA?

DNA contains thymine, while RNA uses uracil. Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

S phase Signup and view all the answers

What is a significant consequence of proofreading during DNA replication?

It prevents mutations from being passed on. Signup and view all the answers

Which process involves copying only select regions of DNA?

Transcription Signup and view all the answers

What occurs during the elongation phase of transcription?

Nucleotide sequences are added to the growing RNA strand. Signup and view all the answers

How do changes in the promoter sequence affect transcription activity?

They can increase or decrease transcription depending on RNA polymerase affinity. Signup and view all the answers

What is one of the least studied areas of RNA biology?

Transcription termination Signup and view all the answers

What role do cellular cues play in RNA polymerase II termination?

They contribute to the regulation of termination, especially under stress. Signup and view all the answers

What consequence can arise from changes in the termination sequences during transcription?

It can lead to the production of RNA transcripts of inappropriate length. Signup and view all the answers

Why is the understanding of RNA polymerase III termination less developed?

It has been overshadowed by the study of RNA polymerase II. Signup and view all the answers

How does a change in DNA sequences affect the transcription process?

Any changes in sequence can lead to alterations in transcription outcomes. Signup and view all the answers

What could be a potential outcome when RNA polymerase affinity for the promoter increases?

It would likely result in enhanced transcription activity. Signup and view all the answers

What can impair the termination process of RNA polymerase II?

Cellular stress conditions. Signup and view all the answers

Study Notes

Gene Regulation

Prokaryotic Gene Regulation is either turning on genes that are off (Positive regulation) or turning off genes that are on (Negative regulation).
Inducer molecules induce expression of a gene. They either block repression or enable activation.
Repressor molecules bind to DNA and prevent transcription.
Co-repressors molecules bind to repressors creating a repressor complex that blocks transcription.
Inhibitors prevent the association of key transcriptional machinery to DNA.
Operon Model involves a key sequence that binds to and blocks the promoter.
Energy Efficiency drives gene regulation. It is more efficient to only produce what is needed.
Environmental Changes necessitate responses for bacteria, e.g. lack of food.
Eukaryotic Gene Regulation is more complex. It involves multiple promoters, enhancers, and transcription factors.
Transcription Factors bind to specific sequences and recruit and orient RNA polymerase to the promoter.
Enhancers can be located on the same chromosome or even on a different chromosome, influencing gene expression through bending or massive complexes.
Regulation of transcription controls the level of association of RNA polymerase to the promoter.
Eukaryotic Gene Regulation predominantly occurs at the level of transcription.
Organization of the genetic material plays a key role in eukaryotic gene regulation.

DNA vs. RNA

DNA contains deoxyribose and RNA contains ribose
DNA exists as a double-stranded helix and RNA exists as a single-stranded helix
DNA uses thymine (T), but RNA uses uracil (U)
DNA is used as a template for RNA synthesis
RNA acts as a primer to initiate DNA synthesis at origins of replication

RNA Structure

RNA can form higher order structures based on its single-stranded nature
RNA can fold back on itself to form stem-loop structures or other complex shapes
RNA can form intramolecular base pairings involving hydrogen bonds

Types of RNA

Ribosomal RNA (rRNA) is the primary component of ribosomes which are responsible for protein synthesis
Messenger RNA (mRNA) carries genetic information from DNA to the ribosomes
Transfer RNA (tRNA) brings amino acids to the ribosomes to make proteins
Small nuclear RNA (snRNA) is transcribed from protein-coding genes and is involved in processing RNA

Polycistronic mRNA

Polycistronic mRNA is a messenger RNA molecule that encodes multiple proteins
Polycistronic mRNA is found in prokaryotes and allows for the coordinated expression of genes involved in the same pathway
Eukaryotes typically have monocistronic mRNA, where one mRNA molecule codes for one protein

Transcription

Transcription is the process of converting DNA into RNA. It involves three main steps: initiation, elongation, and termination.
Sense strand: the DNA strand that has the same sequence as the mRNA, but contains T instead of U.
Antisense strand: the DNA strand that is the template for RNA synthesis. It has the complementary sequence to mRNA.
The promoter is the sequence of DNA that indicates the start of a gene. It is where the RNA polymerase binds to initiate transcription.
Transcription factors are proteins that help RNA polymerase bind to the promoter and initiate transcription.

Prokaryotic Transcription

Prokaryotes use a single RNA polymerase for all types of RNA synthesis
The promoter typically contains a TATA box (-10) and a consensus sequence at -35 (TTGACA)
Transcription initiation and termination are simpler than in eukaryotes

Eukaryotic Transcription

Eukaryotes have three distinct RNA polymerases: RNA polymerase I, II, and III
RNA polymerase I transcribes rRNA genes
RNA polymerase II transcribes protein-coding genes and snRNAs
RNA polymerase III transcribes tRNA and 5S rRNA genes
Eukaryotic promoters are more complex than those in prokaryotes
Transcription initiation involves multiple transcription factors
Termination is more complex than in prokaryotes, with distinct mechanisms for each polymerase.

Transcription Termination

Transcription termination is controlled by termination sequences in DNA and specific proteins
RNA polymerase I uses a protein called TTFI as a termination factor
RNA polymerase II uses a variety of termination factors, including the CTD domain of the polymerase, Xrn2 exonuclease, and termination sequences.
RNA polymerase III termination mechanisms are less characterized.

Impact of Changes in Sequence

Changes in DNA or RNA sequence can affect transcription, RNA structure, and protein function
Changes in the promoter sequence can affect RNA polymerase binding and transcription activity.
Changes in the termination sequences can result in the production of mRNAs of incorrect lengths
Changes in RNA sequence can affect mRNA structure, stability, and translation efficiency.

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Description

This quiz covers key concepts in gene regulation, including mechanisms of prokaryotic and eukaryotic gene expression. Topics include the roles of inducers, repressors, co-repressors, and the operon model, as well as the impact of environmental changes. Test your understanding of how gene regulation contributes to cellular efficiency.