Translation Elongation: Codon Recognition and tRNA Binding
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Questions and Answers

What is the function of the TATA box in transcription initiation?

  • Marks the start of transcription
  • Joins the promoter region of the gene
  • Serves as a crucial binding site for RNA Polymerase II (correct)
  • Synthesizes a complementary RNA strand

    • Which of the following correctly describes the non-coding strand of DNA?

  • Serves as the template for RNA synthesis (correct)
  • Contains Uracil (U) instead of Thymine (T)
  • Marks the end of transcription
  • Is identical to the coding strand

    • What role does RNA Polymerase II play during transcription initiation?

  • Joins at the promoter region of the gene
  • Adds complementary RNA nucleotides
  • Binds to the transcription initiation complex (correct)
  • Synthesizes thymine instead of uracil

    • Which factor marks the beginning of transcription?

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

    During elongation in transcription, what does RNA Polymerase do?

    <p>Adds complementary RNA nucleotides</p> Signup and view all the answers

    Which element is found about 25 nucleotides upstream of a gene and binds to critical factors?

    <p>TATA box</p> Signup and view all the answers

    What happens once the transcription initiation complex is assembled?

    <p>Start of Transcription</p> Signup and view all the answers

    What is an essential role of Transcription Factors in gene expression?

    <p>Decide Whether to Express a Gene or Not</p> Signup and view all the answers

    What invests GTP to ensure accuracy and efficiency during translation elongation?

    <p>Guanosine triphosphate (GTP)</p> Signup and view all the answers

    During peptide bond formation, which ribosomal subunit catalyzes the formation of the bond?

    <p>Large ribosomal subunit</p> Signup and view all the answers

    What happens to the tRNA in the P site during the translocation process in translation?

    <p>Moves to the E site</p> Signup and view all the answers

    Which component recognizes a stop codon during translation termination?

    <p>Release factor</p> Signup and view all the answers

    What is hydrolyzed during the final steps of translation?

    <p>Peptide bond between amino acids</p> Signup and view all the answers

    In translation, which step involves moving the tRNA from the A site to the P site?

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

    What gives the analogy of aligning puzzle pieces for the correct mRNA-tRNA binding?

    <p>$GTP (Guanosine triphosphate)$ investment</p> Signup and view all the answers

    Which analogy is used to describe the recognition of a stop codon during translation termination?

    <p>$Final$ note of a musical piece</p> Signup and view all the answers

    What is the function of the modified guanine nucleotide added during capping?

    <p>Protection from degradation</p> Signup and view all the answers

    What is the main role of the poly-A tail in mRNA processing?

    <p>Protecting mRNA from degradation</p> Signup and view all the answers

    Which process involves the removal of introns from pre-mRNA?

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

    What is the purpose of adding a poly-A tail to the 3’ end of pre-mRNA?

    <p>Protecting mRNA from degradation</p> Signup and view all the answers

    Which component is responsible for facilitating the export of mRNA from the nucleus to the cytoplasm?

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

    What is the main function of splicing in mRNA processing?

    <p>Removing non-coding regions</p> Signup and view all the answers

    In mRNA processing, what does 5’ capping protect the nascent mRNA from?

    <p>Ribonucleases degradation</p> Signup and view all the answers

    Where do proteins destined for the cytosol complete translation?

    <p>On free ribosomes</p> Signup and view all the answers

    What differentiates proteins destined for the endomembrane system from those destined for the cytosol during translation?

    <p>The type of ribosome they complete translation on</p> Signup and view all the answers

    What is the role of signal recognition particle (SRP) in protein synthesis?

    <p>Recognizing the signal peptide</p> Signup and view all the answers

    Which step of protein synthesis involves secretory and membrane proteins taking divergent paths?

    <p>Step 6</p> Signup and view all the answers

    What is the function of fixed ribosomes on the rough ER?

    <p>Specializing in proteins destined for the endomembrane system</p> Signup and view all the answers

    Which organelle solubilizes secretory proteins during protein synthesis?

    <p>Endoplasmic reticulum</p> Signup and view all the answers

    What feature distinguishes free ribosomes from fixed ribosomes?

    <p>Their association with the endomembrane system</p> Signup and view all the answers

    Why are proteins continuously produced and function in the cytosol described as 'independent artisans'?

    <p>They craft proteins without relying on an assembly line</p> Signup and view all the answers

    What is the role of RNA in protein synthesis?

    <p>To act as a messenger to carry the information stored in DNA to make protein</p> Signup and view all the answers

    What is the main function of transcription factors in gene expression?

    <p>Enhancing gene transcription</p> Signup and view all the answers

    What marks the start of transcription for a specific gene?

    <p>Binding of RNA polymerase to a promoter sequence</p> Signup and view all the answers

    Which enzyme recognizes and binds to a promoter sequence near the beginning of a gene during transcription initiation?

    <p>RNA polymerase</p> Signup and view all the answers

    What is the function of repressor transcription factors in gene expression?

    <p>Decreasing gene transcription</p> Signup and view all the answers

    Which type of proteins help determine which genes are turned on or off by binding to nearby DNA?

    <p>Transcription factors</p> Signup and view all the answers

    In protein synthesis, what comes after the process of transcription?

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

    Study Notes

    Transcription Initiation

    • The assembly of transcription factors, including the TATA box binding protein (TBP), forms the transcription initiation complex.
    • The TATA box, located about 25 nucleotides upstream of the gene, serves as a crucial binding site for these factors.
    • TBP is part of a larger protein complex that includes RNA Polymerase II.
    • Once assembled, this complex marks the start of transcription.

    Initiation of Transcription

    • With the transcription initiation complex in place, RNA Polymerase II binds to it.
    • Additional transcription factors also join at the promoter region of the gene.
    • This binding signifies the beginning of transcription.
    • RNA Polymerase II reads the DNA template strand, synthesizing a complementary RNA strand.

    Coding and Non-Coding Strands

    • The coding strand of DNA has the same sequence as the RNA transcript, except with Thymine (T) instead of Uracil (U).
    • The non-coding strand, also known as the template strand, serves as the template for RNA synthesis.

    Elongation

    • Once initiated, RNA polymerase begins moving downstream along the gene.
    • It reads the DNA strand and adds complementary RNA nucleotides to the growing mRNA (messenger RNA) chain.
    • During this process, RNA uses Uracil (U) instead of Thymine (T), pairing Adenine (A) with Uracil.

    Gene Expression

    • Gene expression is the process of going from DNA to a functional product (protein).
    • DNA → RNA → Protein is the sequence of gene expression.
    • Genotype refers to an organism's hereditary information, while phenotype refers to the actual observable or physiological traits.
    • Genotype and its interactions with the environment determine the phenotype.

    Transcription Factors

    • Transcription factors are proteins that play a pivotal role in regulating gene expression.
    • They help determine which genes are turned on or off by binding to nearby DNA.
    • Activator transcription factors enhance gene transcription, while repressor factors decrease it.

    Processing of Pre-mRNA to Mature mRNA

    • Capping involves adding a modified guanine nucleotide to the 5' end of the pre-mRNA transcript, which serves several critical functions, including protection, ribosome binding, and export.
    • Tailing involves adding a sequence of 50 to 250 adenine nucleotides (poly-A tail) to the 3' end of the pre-mRNA transcript, which protects the mRNA from degradation, assists in transporting the mature mRNA, and is involved in binding proteins that initiate translation.
    • Splicing is the process of removing introns (non-coding regions) from the pre-mRNA transcript, ensuring efficient resource utilization and contributing to cellular specialization and adaptation.

    Protein Synthesis and Vesicular Transport

    • Proteins destined for the cytosol are continuously produced and function in the cytosol, completing translation on free ribosomes.
    • Proteins destined for the endomembrane system complete translation at fixed ribosomes on the rough ER (RER).
    • The ribosome's location determines its function, with fixed ribosomes on the RER specialized for proteins destined for the endomembrane system.
    • Signal peptide and signal recognition particle (SRP) are involved in the targeting of proteins to the endomembrane system.

    Translation Elongation

    • The ribosome reads the mRNA codon in the A site, and the anticodon of the incoming tRNA base pairs with the mRNA codon.
    • GTP is invested to ensure accuracy and efficiency.
    • The large ribosomal subunit catalyzes the formation of a peptide bond, linking the incoming amino acid to the growing polypeptide chain.

    Translation Termination

    • When a stop codon (UAA, UAG, or UGA) enters the A site, it's recognized by a release factor.
    • The release factor fits neatly into the P site, and the bond between the P-site tRNA and the last amino acid is hydrolyzed.
    • This marks the end of translation.

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    Gene to Protein PDF

    Description

    Test your knowledge on the process of translation elongation, focusing on codon recognition and tRNA binding. Learn how the ribosome acts as a precision instrument and how GTP is used for accuracy and efficiency. Explore the analogy of aligning puzzle pieces for a better understanding of peptide bond formation.

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