RNA Types and Transcription Processes
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Questions and Answers

Which RNA type is primarily responsible for carrying genetic information?

  • tRNA
  • rRNA
  • mRNA (correct)
  • snRNA

What is the role of rho protein during prokaryotic transcription termination?

  • To form the GC hairpin loop
  • To synthesize rRNA during elongation
  • To initiate RNA synthesis at the promoter
  • To bind to the rut site and cause termination (correct)

What triggers the initiation of eukaryotic transcription?

  • Binding of RNA polymerase II directly to the gene
  • The presence of exons in the mRNA
  • Splicing of hnRNA
  • Transcription factors binding to the TATA box (correct)

During the elongation phase of transcription, what is primarily synthesized?

<p>hnRNA (D)</p> Signup and view all the answers

Which of the following describes the process of splicing?

<p>Joining exons together while removing introns (A)</p> Signup and view all the answers

Which RNA polymerase is responsible for synthesizing mRNA in eukaryotic cells?

<p>RNA Polymerase II (C)</p> Signup and view all the answers

What is the function of the 5' cap added during hnRNA processing?

<p>To protect the RNA from degradation and aid in recognition by ribosomes (D)</p> Signup and view all the answers

What sequence signals the end of transcription in eukaryotes?

<p>AAUAAA polyadenylation signal (A)</p> Signup and view all the answers

In prokaryotic transcription, what occurs at the Pribnow box?

<p>Binding of RNA polymerase holoenzyme (D)</p> Signup and view all the answers

Which of the following sequences is typically associated with Rho-dependent termination in prokaryotic transcription?

<p>rut site (B)</p> Signup and view all the answers

What is the primary function of snRNA in the context of eukaryotic transcription?

<p>Catalyze splicing (B)</p> Signup and view all the answers

What occurs during the elongation phase of prokaryotic transcription?

<p>Synthesis of RNA from rNTPs (B)</p> Signup and view all the answers

After hnRNA undergoes splicing, what is the final product?

<p>Mature mRNA (C)</p> Signup and view all the answers

Which of the following best describes the role of RNA polymerase I in eukaryotic cells?

<p>Synthesizes rRNA (D)</p> Signup and view all the answers

Which RNA type is involved in translating the genetic code into amino acids during protein synthesis?

<p>tRNA (A)</p> Signup and view all the answers

What mechanism is primarily responsible for the cleavage of RNA downstream of the polyadenylation signal in eukaryotic transcription termination?

<p>Endonucleolytic cleavage (A)</p> Signup and view all the answers

In eukaryotic transcription initiation, which complex binds to the TATA box?

<p>TFIID with TBP (D)</p> Signup and view all the answers

What structural formation occurs during eukaryotic splicing as introns are removed?

<p>Lariat structure (C)</p> Signup and view all the answers

What is the primary product formed during the elongation phase of eukaryotic transcription?

<p>hnRNA (B)</p> Signup and view all the answers

Which RNA polymerase in eukaryotes is responsible for the synthesis of tRNA?

<p>RNA Polymerase III (B)</p> Signup and view all the answers

What structural feature is formed during splicing when introns are removed?

<p>Lariat structure (D)</p> Signup and view all the answers

In prokaryotic transcription, what is the role of the sigma factor in the initiation process?

<p>It assists RNA polymerase in binding to the promoter. (B)</p> Signup and view all the answers

What is the primary function of the poly-A tail added during hnRNA processing?

<p>To provide stability and facilitate export from the nucleus. (B)</p> Signup and view all the answers

Which of the following statements regarding eukaryotic transcription factors is true?

<p>They assist in the binding of RNA polymerase to the promoter region. (A)</p> Signup and view all the answers

Which process occurs during rho-dependent termination in prokaryotic transcription?

<p>Binding of the Rho protein to the rut site. (B)</p> Signup and view all the answers

What is the primary role of snRNPs in eukaryotic transcription?

<p>To catalyze the splicing of pre-mRNA. (C)</p> Signup and view all the answers

What function does rRNA serve within a cell?

<p>Forms the structural and functional components of ribosomes (C)</p> Signup and view all the answers

Which of the following correctly describes the termination process during prokaryotic transcription?

<p>Termination can occur through both Rho-independent and Rho-dependent mechanisms (A)</p> Signup and view all the answers

What is the primary role of the polyadenylation signal in eukaryotic transcription?

<p>To ensure proper termination of transcription (D)</p> Signup and view all the answers

During splicing of hnRNA, what occurs after the formation of a lariat structure?

<p>Introns are excised and exons are joined together (C)</p> Signup and view all the answers

Which factor is primarily responsible for recruiting RNA polymerase II during eukaryotic transcription initiation?

<p>TFIID with TBP (A)</p> Signup and view all the answers

What role does the 5' cap play in the processing of hnRNA?

<p>Stabilizes the mRNA and assists in ribosome recognition (A)</p> Signup and view all the answers

In eukaryotic cells, which RNA polymerase is responsible for synthesizing rRNA?

<p>RNA Polymerase I (B)</p> Signup and view all the answers

What is a distinguishing feature of Rho-independent transcription termination in prokaryotes?

<p>Involves a GC-rich hairpin loop followed by a U-rich sequence (C)</p> Signup and view all the answers

What is the significance of hnRNA (pre-mRNA) in eukaryotic cells?

<p>It contains both introns and exons before processing into mature mRNA (C)</p> Signup and view all the answers

Flashcards

mRNA function

Carries genetic code for protein synthesis.

tRNA function

Transfers amino acids to ribosomes.

rRNA function

Forms the ribosome structure.

Prokaryotic RNA polymerase initiation

RNA polymerase holoenzyme binds the Pribnow box.

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Eukaryotic transcription factor

TFIID with TBP binds to the TATA box to recruit RNA polymerase II

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hnRNA processing - capping

Protection and ribosome recognition.

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hnRNA processing - polyadenylation

3' end stability with a poly-A tail.

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Splicing in hnRNA

Introns removed, exons joined by snRNPs.

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RNA polymerase I

Synthesizes rRNA - major component of the ribosome.

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What are the main types of RNA?

There are four primary types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), and small nuclear RNA (snRNA). Each plays a crucial role in protein synthesis.

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What happens during prokaryotic transcription initiation?

The RNA polymerase holoenzyme, consisting of the core enzyme and the sigma factor, binds to the Pribnow box in the promoter region of the DNA, initiating transcription.

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What are the two types of prokaryotic transcription termination?

Transcription can terminate in two ways: Rho-independent and Rho-dependent. In Rho-independent termination, a GC-rich hairpin loop and a U-rich sequence cause RNA polymerase to detach. In Rho-dependent termination, the Rho protein recognizes a specific sequence (rut site) and stops transcription.

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What is the main difference between prokaryotic and eukaryotic transcription initiation?

In eukaryotes, transcription factors like TFIID with TBP bind to the TATA box in the promoter region, recruiting RNA polymerase II. In prokaryotes, only the holoenzyme binds to the promoter.

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How is hnRNA processed into mature mRNA?

hnRNA undergoes three main processing steps: capping, polyadenylation, and splicing. A 5' cap is added for stability and ribosome recognition. A poly-A tail is added to the 3' end for stability. Splicing removes introns and joins exons using snRNPs.

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How does eukaryotic transcription termination occur?

A polyadenylation signal (AAUAAA) sequence signals the end of transcription. Cleavage occurs downstream of this signal, and a poly-A tail is added.

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What are the three RNA polymerases in eukaryotes?

Eukaryotes have three main RNA polymerases: Polymerase I synthesizes rRNA, Polymerase II synthesizes mRNA, and Polymerase III synthesizes tRNA and 5S rRNA.

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What is the purpose of splicing?

Splicing removes non-coding sequences called introns from hnRNA. This leaves only the coding sequences, called exons, which are then joined together to form mature mRNA.

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Describe the lariat structure formed during splicing.

During splicing, the intron is looped out, creating a lariat structure resembling a lasso. The lariat is then removed, and the exons are joined together.

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What is the role of the sigma factor in prokaryotic transcription?

The sigma factor is a component of the RNA polymerase holoenzyme in prokaryotes. It helps the enzyme recognize and bind to the promoter region of DNA, initiating transcription.

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What is the Pribnow box?

The Pribnow box is a specific sequence of DNA located in the promoter region of prokaryotic genes. It acts as a recognition site for the RNA polymerase holoenzyme, marking the start point for transcription.

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Describe Rho-independent termination

Rho-independent termination is a mechanism of transcription termination in prokaryotes. It occurs when a GC-rich hairpin loop and a U-rich sequence in the RNA transcript cause the RNA polymerase to detach from the DNA.

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Describe Rho-dependent termination

Rho-dependent termination is another mechanism of transcription termination in prokaryotes. It involves the Rho protein, which binds to a specific site on the RNA transcript (rut site) and stops transcription.

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What is the role of TFIID in eukaryotic transcription?

TFIID is a transcription factor in eukaryotes that binds to the TATA box in the promoter region. It recruits RNA polymerase II to the start site of transcription.

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What is hnRNA?

hnRNA, also known as pre-mRNA, is the initial RNA transcript produced during eukaryotic transcription. It contains both introns and exons.

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What is the purpose of the 5' cap?

The 5' cap is a modified guanine nucleotide added to the 5' end of hnRNA. It provides stability and helps the ribosome recognize the mRNA for translation.

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What is the function of snRNPs in splicing?

snRNPs are small nuclear ribonucleoproteins that play a crucial role in splicing. They recognize and bind to specific sequences in pre-mRNA and remove introns, joining exons to create mature mRNA.

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RNA Types

There are 4 main types of RNA involved in protein synthesis: mRNA carries genetic information, tRNA transfers amino acids, rRNA forms ribosomes, snRNA involved in splicing.

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Prokaryotic Transcription Initiation

RNA polymerase binds to the Pribnow box in the promoter region to begin transcribing DNA into RNA in prokaryotes.

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Prokaryotic Transcription Termination: Rho-Independent

Involves a hairpin loop and U-rich region in the RNA transcript that cause the polymerase to detach.

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Prokaryotic Transcription Termination: Rho-Dependent

The Rho protein binds to a specific site on the RNA transcript (rut site) and separates the RNA from the polymerase.

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Eukaryotic Transcription Initiation

Transcription factors like TFIID bind to the TATA box in the promoter region, recruiting RNA Polymerase II to initiate transcription.

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Eukaryotic Transcription Termination

The Polyadenylation signal (AAUAAA) signals the end of transcription, followed by RNA cleavage downstream.

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hnRNA Processing: Splicing

Introns are removed, and exons are joined together by snRNPs to create mature mRNA.

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Study Notes

RNA Types

  • mRNA: Carries genetic information
  • tRNA: Transfers amino acids during translation
  • rRNA: Forms ribosomes
  • snRNA: Involved in splicing

Prokaryotic Transcription

  • Initiation: RNA polymerase holoenzyme (core enzyme + sigma factor) binds the Pribnow box in the promoter region.
  • Elongation: Core RNA polymerase synthesizes RNA by adding rNMPs.
  • Termination:
    • Rho-Independent: GC hairpin loop and U-rich sequence cause detachment of RNA polymerase.
    • Rho-Dependent: Rho protein binds to the rut site, stopping transcription.

Eukaryotic Transcription

  • Initiation: Transcription factors like TFIID with TBP bind promoter elements (TATA box), recruiting RNA Polymerase II.
  • Elongation: Produces hnRNA (pre-mRNA) that includes introns.
  • Termination: Polyadenylation signal (AAUAAA) sequence signals the end of transcription; cleavage occurs downstream.

RNA Polymerases in Eukaryotes

  • Polymerase I: Synthesizes rRNA
  • Polymerase II: Synthesizes mRNA
  • Polymerase III: Synthesizes tRNA and 5S rRNA

hnRNA Processing to Form Mature mRNA

  • Capping: 5' cap added for stability and ribosome recognition.
  • Polyadenylation: Poly-A tail added to 3' end for stability.
  • Splicing: Introns are removed, and exons are joined by snRNPs, forming a lariat structure.

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Description

This quiz covers the various types of RNA and their functions, as well as the detailed processes of prokaryotic and eukaryotic transcription. You will learn about the roles of mRNA, tRNA, rRNA, and how transcription is initiated, elongated, and terminated in both cell types.

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