RNA and Transcription Overview

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Questions and Answers

Which RNA polymerase is responsible for synthesizing ribosomal rRNA genes in eukaryotes?

  • RNA polymerase III
  • RNA polymerase IV
  • RNA polymerase II
  • RNA polymerase I (correct)

Which type of RNA is synthesized by RNA polymerase II in eukaryotic cells?

  • Messenger RNA (mRNA) (correct)
  • Transfer RNA (tRNA)
  • Ribosomal RNA (rRNA)
  • Small nuclear RNA (snRNA)

What is the main role of the promoter region in gene transcription?

  • It encodes the amino acid sequence of proteins.
  • It prevents the binding of ribosomes to mRNA.
  • It acts as a binding site for RNA polymerase and transcription factors. (correct)
  • It assists in the polyadenylation of mRNA.

Which process involves the addition of a poly-A tail to the 3' end of mRNA?

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

Which type of RNA is not directly involved in translating genetic information into protein?

<p>Micro RNA (miRNA) (A)</p> Signup and view all the answers

What is the role of enhancers in gene expression?

<p>They upregulate transcription from a distance. (A)</p> Signup and view all the answers

Which statement about silencers is correct?

<p>Silencers inhibit transcription similar to how enhancers activate it. (C)</p> Signup and view all the answers

What is the first step required in mRNA processing?

<p>Synthesis of the primary RNA transcript. (D)</p> Signup and view all the answers

What is one function of the mediator protein in transcription?

<p>It assists in assembling proteins needed for transcription. (C)</p> Signup and view all the answers

Which process is primarily responsible for adding a protective cap to the mRNA?

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

What is the primary role of polyadenylation in mRNA processing?

<p>It stabilizes the mature mRNA and facilitates its export from the nucleus. (C)</p> Signup and view all the answers

Which RNA type primarily serves as the template for protein synthesis?

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

Which step in mRNA processing occurs after transcription and involves the addition of a protective structure at the 5' end?

<p>5' capping (D)</p> Signup and view all the answers

What is the function of tRNA in protein synthesis?

<p>It carries amino acids to the ribosome. (A)</p> Signup and view all the answers

Which of the following processes involves the removal of non-coding sequences from pre-mRNA?

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

Which molecule is primarily composed of rRNA and proteins, and functions as the site of protein synthesis?

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

What is the first step that occurs during transcription initiation?

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

What is the consequence of failing to add the 5' cap to newly synthesized mRNA?

<p>Decreased efficiency of translation. (A)</p> Signup and view all the answers

Flashcards

Polyadenylation

The process of adding a tail of adenine nucleotides to the 3' end of a pre-mRNA molecule.

CPSF (Cleavage and Polyadenylation Specificity Factor)

A protein that binds to the 3' end of the pre-mRNA and recruits other proteins involved in polyadenylation.

CstF (Cleavage Stimulation Factor)

A protein that binds to the 3' end of the pre-mRNA and helps recruit other proteins involved in polyadenylation.

Poly-A polymerase

The enzyme that adds adenine nucleotides to the 3' end of the pre-mRNA.

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Pre-mRNA

The primary transcript of a gene that hasn't been processed yet.

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mRNA (Messenger RNA)

RNA that is used to make proteins.

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rRNA (Ribosomal RNA)

RNA that makes up ribosomes, the machinery for protein synthesis.

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tRNA (Transfer RNA)

RNA that carries amino acids to the ribosomes for protein synthesis.

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RNA polymerase

A multi-unit enzyme that synthesizes new RNA from DNA templates.

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RNA polymerase I

A type of RNA polymerase responsible for transcribing rRNA genes, which are crucial for ribosome assembly.

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RNA polymerase II

A type of RNA polymerase responsible for transcribing protein-coding genes into messenger RNA (mRNA).

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RNA polymerase III

A type of RNA polymerase responsible for transcribing tRNA genes, 5S rRNA genes, and some miRNA genes.

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Svedberg unit (S)

A unit used to measure the sedimentation rate of molecules, reflecting their size and shape. Larger molecules have higher S values.

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Enhancers

DNA sequences that can activate transcription of a gene. They can be located far away from the promoter, either upstream or downstream of the gene.

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Silencers

DNA sequences that repress transcription of a gene. They act like brakes on gene expression.

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mRNA processing

The process of converting a primary transcript (pre-mRNA) into a mature mRNA molecule. This involves modifications like capping, splicing, and polyadenylation.

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Activators

Proteins that bind to enhancers and help recruit other proteins to activate transcription.

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Mediator

A protein complex that helps assemble the proteins needed for transcription initiation.

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Study Notes

RNA and Transcription

  • RNA differs from DNA in its sugar (ribose vs. deoxyribose) and the presence of uracil instead of thymine
  • Transcription is the process of creating RNA from a DNA template
  • Transcription involves the formation of complementary base pairs of RNA using an antisense DNA template
  • Transcription is carried out by RNA polymerase enzymes
  • Eukaryotic cells have three RNA polymerases: RNA polymerase I (ribosomal rRNA genes), RNA polymerase II (protein-coding genes, messenger RNA, some microRNAs), and RNA polymerase III (transfer RNA, 5S rRNA, some microRNAs)
  • Promoters contain control regions
  • Promoters contain sequences that bind to transcription machinery
  • A common initiator element is around the transcription start site (e.g., -1 (C) and +1 (A))
  • A TATA box is around 25-35 base pairs upstream of the transcription start site
  • Several types of RNA exist: ribosomal RNA (rRNA) to make ribosomes, messenger RNA (mRNA) to act as an intermediary code, and transfer RNA (tRNA) to carry amino acids
  • mRNA is processed by splicing out introns, capping at the 5' end, and polyadenylation at the 3' end
  • Introns are not expressed and translated to proteins
  • Exons are expressed and make proteins
  • Enhancers activate transcription while silencers repress transcription; these can be quite far from the promoter region
  • RNA polymerase I manufactures ribosomal RNA
  • RNA polymerase II produces messenger RNA and some non-coding RNA molecules
  • RNA polymerase III generates transfer RNA and other small RNAs

mRNA Processing

  • The first step in mRNA production is making the RNA from the DNA.
  • mRNA processing involves several crucial steps to create mature mRNA molecules from the primary transcript:
    • Capping: Adding a 5' cap to the 5' end of the mRNA molecule provides a signal and protection against degradation
    • Splicing: Removing non-coding introns from the pre-mRNA and joining the coding exons; this step is crucial to creating the correct protein sequence
    • Polyadenylation: Adding a poly(A) tail to the 3' end of the mRNA molecule improves stability, facilitates export, and enables ribosomes to recognize and translate the mRNA

Ribosomes

  • The ribosome is the site of translation
  • The ribosome is a complex protein machine made of many proteins and rRNA
  • Ribosomes have four different binding sites (1 for mRNA, and 3 for tRNA)

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BB1725 Lecture 6 RNA and transcription (4) PDF

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