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L7 Translation
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L7 Translation

Created by
@TimeHonoredLimerick2759

Questions and Answers

Which component is NOT considered part of the translation machinery?

  • Ribosomes
  • Transfer RNAs
  • Messenger RNAs
  • DNA polymerase (correct)

    • The central dogma of molecular biology includes the processes of transcription and replication.

    False

    What is the primary function of tRNAs in translation?

  • To deliver amino acids and decode mRNA codons (correct)
  • To degrade mRNA
  • To provide energy for translation
  • To form peptide bonds

    • What are the three main stages of translation?

    <p>Initiation, elongation, termination</p> Signup and view all the answers

    The ribosome has only one binding site for tRNAs.

    <p>False</p> Signup and view all the answers

    Translation occurs in the ______ of the cell.

    <p>cytoplasm</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Ribosomes = Sites of protein synthesis tRNAs = Carry amino acids to the ribosome mRNAs = Versatile carriers of genetic information rRNAs = Structural and functional components of ribosomes</p> Signup and view all the answers

    What is the role of the ribosomal RNA in peptide bond formation?

    <p>It acts like an enzyme.</p> Signup and view all the answers

    The energy required to add the amino acid during translation primarily comes from _____ hydrolysis.

    <p>GTP</p> Signup and view all the answers

    What best defines the term 'translation' in molecular biology?

    <p>The synthesis of proteins from mRNA</p> Signup and view all the answers

    Match the tRNA binding sites with their functions:

    <p>A site = Holds the tRNA charged with the growing peptide chain P site = Accepts the incoming aminoacyl tRNAs E site = Holds the tRNA that previously donated its amino acid</p> Signup and view all the answers

    How does the ribosome ensure translational fidelity?

    <p>By recognizing the correct codon-anticodon interaction in a wider structural context</p> Signup and view all the answers

    What is the role of eIF2a phosphorylation in the cellular response?

    <p>It integrates the response to multiple stresses.</p> Signup and view all the answers

    The 5' methylated GTP cap is essential for regulating mRNA stability.

    <p>True</p> Signup and view all the answers

    What does GCN4 represent in yeast?

    <p>It is the yeast homologue of mammalian ATF4.</p> Signup and view all the answers

    The ___ tail affects mRNA stability and is composed of 100-200 adenosine residues.

    <p>Poly A</p> Signup and view all the answers

    Match the components of mRNA with their functions:

    <p>5' Methylated GTP Cap = Regulates nuclear export of mRNA 3' UTR = Controls mRNA stability and translation efficiency 5' UTR = Helps initiate ribosome binding IRES = Allows independent translation without Cap recognition</p> Signup and view all the answers

    What is one result of translational reprogramming during stress?

    <p>Improved cell function by reallocating resources.</p> Signup and view all the answers

    The 3' UTR is responsible for promoting the binding of eIF4E.

    <p>False</p> Signup and view all the answers

    What does uORF stand for and what is its significance in translation?

    <p>Upstream Open Reading Frame; it regulates GCN4 translation by promoting 40S dissociation.</p> Signup and view all the answers

    What is the primary role of transfer RNAs (tRNAs) in translation?

    <p>To decode mRNA codon sequences and deliver amino acids</p> Signup and view all the answers

    The ribosomes move from the 3’ end to the 5’ end of the mRNA during translation.

    <p>False</p> Signup and view all the answers

    What are the three key stages of translation?

    <p>Initiation, Elongation, Termination</p> Signup and view all the answers

    The ribosomal _____ catalyzes the formation of peptide bonds between amino acids.

    <p>peptidyl transferase</p> Signup and view all the answers

    Match the following structures with their functions in translation:

    <p>mRNA = Template for protein synthesis tRNA = Brings amino acids to the ribosome Ribosome = Site of peptide bond formation eIF4E = Binds the 5' cap of mRNA</p> Signup and view all the answers

    What component of the ribosome is primarily responsible for positioning substrates for peptide bond formation?

    <p>28S rRNA</p> Signup and view all the answers

    The wobble hypothesis allows a single tRNA to recognize multiple codons.

    <p>True</p> Signup and view all the answers

    What is the main purpose of the 5' methylated GTP cap on mRNA?

    <p>To regulate nuclear export, stability, and translation initiation of mRNA</p> Signup and view all the answers

    The _____ position in the codon allows for non-Watson-Crick base pairing in the wobble hypothesis.

    <p>3’</p> Signup and view all the answers

    Which factor is involved in scanning the mRNA for the start codon during translation initiation?

    <p>eIF3</p> Signup and view all the answers

    What is the primary function of internal ribosome entry sites (IRES)?

    <p>To recruit ribosomes without scanning from the cap</p> Signup and view all the answers

    Viruses do not utilize IRES for protein translation.

    <p>False</p> Signup and view all the answers

    What effect does phosphorylation of eEF1A and eEF1B have on translation elongation?

    <p>It enhances the rate of GEF activity and increases the rate of aa-tRNA recruitment.</p> Signup and view all the answers

    The primary protein that is crucial for the recruitment of the 40S ribosomal subunit in cap-independent translation is encoded by the ______.

    <p>IRES</p> Signup and view all the answers

    Which process is crucial for viral replication?

    <p>Translation of viral proteins</p> Signup and view all the answers

    Match the following factors to their roles in translation:

    <p>eIFs = Canonical initiation factors involved in translation ITAFs = Alternative factors for IRES-mediated translation eEF1A = Enhances the recruitment of aa-tRNA during elongation IRES = Enables cap-independent translation</p> Signup and view all the answers

    Phosphorylation of eEF1A leads to a decrease in the rate of tRNA re-binding.

    <p>False</p> Signup and view all the answers

    What role does the integrated stress response play in viral infection?

    <p>It triggers the translation of viral proteins over host proteins.</p> Signup and view all the answers

    Study Notes

    Overall Learning Outcomes

    • Understand molecular mechanisms of translation: initiation, elongation, and termination.
    • Describe regulation of translation stages at a molecular level with specific examples.
    • Explain internal mRNA structures and their contribution to translation regulation.

    Objectives-Part 1

    • Review core concepts of translation.
    • Identify primary components: Ribosomes, Transfer RNAs (tRNAs), and Messenger RNAs (mRNAs).

    Central Dogma

    • Central dogma explains the flow of genetic information: DNA → RNA → Protein.
    • Reverse transcription can occur (e.g., in HIV).

    Adaptor Hypothesis

    • Each amino acid associates chemically with an enzyme, linking to a nucleic acid template.

    Translation Process

    • Ribosomes translate mRNA from the 5’ to 3’ end.
    • Amino acids are delivered by tRNAs with complementary anticodon sequences.
    • Peptide bonds form between amino acids at the ribosome.

    The Ribosome

    • Facilitates translation by catalyzing peptide bond formation.
    • Comprised of two subunits: small (40S) "reads RNA" and large (60S) "joins amino acids."

    Ribosomal Peptidyl Transferase

    • Catalyzes peptide bond formation with enhanced activity through correct substrate positioning.

    Mechanisms of Ribosome Activity

    • Increases peptide bond formation rate by 10^7 times.
    • 28S rRNA and specific ribosomal proteins ensure correct substrate positioning.
    • Hydrogen bonding between tRNA and amino group is crucial for proton transfer during bond formation.

    Transfer RNAs (tRNAs)

    • Decode mRNA codons and deliver corresponding amino acids to ribosome.
    • Possess a "cloverleaf structure" with amino acids attached at the 3’ end.

    Wobble Hypothesis

    • Allows non-Watson-Crick base pairing in the 3’ position of codons, enabling a single tRNA to recognize multiple codons.
    • Reduces the number of required tRNA species.

    Structure of a Typical mRNA

    • Internal Ribosome Entry Site (IRES) allows cap-independent translation.
    • 5' methylated GTP cap regulates export and stability, critical for initiation.
    • 3’ Poly A tail (100-200 adenosines) enhances mRNA stability.

    Key Steps in Translation Initiation

    • 40S ribosomal subunit binds with eIFs to form the 43S complex.
    • The complex targets the 5’ end of mRNA and scans for AUG stop codon.
    • The 60S subunit associates, initiating translation upon AUG recognition.

    Eukaryotic Initiation Factors (eIFs)

    • eIF1/1A and eIF3 attach to 40S subunit facilitating assembly.
    • eIF2/met-tRNA complex forms with GTP as energy source.
    • eIF4E binds to mRNA cap, with eIF4G promoting circularization.

    Translation Elongation

    • tRNAs decode codons and deliver amino acids while forming peptide bonds.
    • Ribosome contains three tRNA binding sites: A site (incoming tRNA), P site (growing peptide), and E site (exit for tRNAs).

    Translation Fidelity

    • The ribosome selects correct tRNA through a broader structural context.
    • Error rate for tRNA selection is between 10^-3 and 10^-4.

    Energy Requirements

    • GTP hydrolysis provides energy for amino acid activation and peptide bond formation.

    Translational Reprogramming in Stress

    • Limits resource usage during stress and reprograms translation of specific transcripts for cell function improvement.

    uORF Regulation of GCN4 Translation

    • Involves ternary complex availability for scanning start codons, impacting translation efficiency.

    IRES in Cap-Independent Translation

    • IRES structures can recruit ribosomes independently of cap, engaging alternative initiation factors.

    Viral Use of IRES

    • Viruses utilize IRES for protein translation during stress, enhancing their replication efficiency.

    Regulation of Translation Elongation

    • Phosphorylation of eEF1A and eEF1B increases the rate of aminoacyl-tRNA recruitment, enhancing translation efficiency.

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    Description

    Test your knowledge on the translation machinery in molecular biology. This quiz covers key concepts such as the function of tRNAs, the stages of translation, and the components involved in this vital biological process. Perfect for students learning about the central dogma.

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