Biology Translation Process
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Questions and Answers

What does a codon consist of?

  • A sequence of 2 nucleotides
  • A sequence of 3 nucleotides (correct)
  • A sequence of 4 nucleotides
  • A sequence of 5 nucleotides

    • What is meant by the degeneracy of the genetic code?

  • All amino acids are encoded by a single codon
  • Codons code for the same amino acid in different organisms
  • Each codon can encode multiple proteins
  • Each amino acid is encoded by multiple codons (correct)

    • What consequence does a frame-shift mutation typically have?

  • Only affects non-coding regions
  • No effect on protein synthesis
  • Results in a truncated protein or alternative amino acid sequence (correct)
  • Preserves the reading frame of mRNA

    • Which of the following diseases is associated with trinucleotide repeat expansion?

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

    What characterizes the genetic code as being 'comma-less'?

    <p>There are no sequences that interrupt the reading frame (D)</p> Signup and view all the answers

    Which mutation is characterized by the deletion of one or more nucleotides?

    <p>Frame-shift mutation (B)</p> Signup and view all the answers

    Which aspect of the genetic code indicates that the code can be interpreted in different ways without changing the protein sequence?

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

    What is the primary effect of the mutation deletion known as DF508 in cystic fibrosis?

    <p>Loss of protein structure leading to dysfunctional channels (A)</p> Signup and view all the answers

    What is the role of aminoacyl-tRNA synthetase in protein synthesis?

    <p>Catalyzes the addition of amino acids to specific tRNA (A)</p> Signup and view all the answers

    Which step in protein translation involves the assembly of the components before peptide bond formation?

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

    What molecule carries the anticodon that base-pairs with the mRNA codon during translation?

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

    Which of the following is a posttranslational modification?

    <p>Phosphorylation of amino acids (A)</p> Signup and view all the answers

    What terminates protein synthesis in the elongation process?

    <p>A termination codon entering the A site (A)</p> Signup and view all the answers

    How many high energy bonds are broken for each amino acid added during protein synthesis?

    <p>4 (D)</p> Signup and view all the answers

    What does the 3' CCA sequence on tRNA do?

    <p>Acts as a site for amino acid attachment (A)</p> Signup and view all the answers

    Which component is primarily responsible for the formation of peptide bonds during translation?

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

    What is the role of the 5’ cap added to the primary transcript during RNA processing?

    <p>It protects the RNA from degradation. (D)</p> Signup and view all the answers

    What specifically is a spliceosome composed of?

    <p>Small nuclear RNAs and proteins. (D)</p> Signup and view all the answers

    Which part of the RNA processing involves the addition of a poly(A) tail?

    <p>Cleavage downstream of the polyadenylation signal. (A)</p> Signup and view all the answers

    What occurs during the formation of the basal transcription complex?

    <p>Multiple proteins and transcription factors are involved. (A)</p> Signup and view all the answers

    How is the primary transcript different from the mature mRNA found in the cytoplasm for translation?

    <p>It includes introns that require processing. (A)</p> Signup and view all the answers

    What is the role of promoters in gene expression?

    <p>They select the start site of RNA synthesis. (A)</p> Signup and view all the answers

    Which sequences are essential for splicing introns from the primary RNA transcript?

    <p>Splice acceptor and donor sequences (B)</p> Signup and view all the answers

    What is the primary product of protein-encoding genes?

    <p>Messenger RNA (mRNA) (D)</p> Signup and view all the answers

    What are the untranslated regions (UTR) of mRNA responsible for?

    <p>Regulating stability and translational efficiency. (D)</p> Signup and view all the answers

    Where does RNA synthesis occur within the cell?

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

    How are RNA polymers synthesized during transcription?

    <p>By RNA polymerase enzymes (C)</p> Signup and view all the answers

    Which of the following statements about RNA processing is true?

    <p>mRNA is modified before translation into proteins. (A)</p> Signup and view all the answers

    What is the primary function of microRNA (miRNA)?

    <p>To regulate gene expression post-transcriptionally. (D)</p> Signup and view all the answers

    Flashcards

    Genetic Code

    How proteins with 20 amino acids are coded by mRNA with 4 nucleotides.

    Codon

    A sequence of 3 nucleotides that codes for an amino acid.

    Reading Frame

    The way nucleotides are grouped into codons in mRNA.

    Point Mutation

    A change in a single nucleotide in DNA.

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    Frame-Shift Mutation

    Addition or deletion of a nucleotide in DNA, changing the reading frame.

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    Genetic Code Characteristics

    Specific to a species, almost universal, multiple codons code for most amino acids, non-overlapping, and commaless.

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    Trinucleotide Repeat Expansion

    A sequence of 3 bases amplified, often in coding regions, leading to extra amino acids and disorders

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    Consequences of Mutations

    Mutations can lead to changes in protein sequence, or stop the production of proteins, often leading to diseases.

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    CFTR protein mutation

    A loss of phenylalanine (Phe) at position 508 in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein.

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    Protein Synthesis components

    Protein synthesis needs amino acids, transfer RNA (tRNA), aminoacyl-tRNA synthetases, messenger RNA (mRNA), ribosomes, protein factors, and energy (ATP and GTP).

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    tRNA structure

    tRNA has an amino acid attachment site (3' CCA) and an anticodon that base pairs with a complementary codon on mRNA.

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    Aminoacyl-tRNA synthetase

    An enzyme that attaches the correct amino acid to its specific tRNA.

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    Ribosome function

    Ribosomes are the sites of protein synthesis, made of rRNA and proteins, and have binding sites for tRNA.

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    Protein Translation steps

    Protein translation has three major stages: initiation (assembly), elongation (adding amino acids sequentially), and termination (stopping the chain).

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    Post-translational modification

    Changes to a polypeptide chain after it's made, such as trimming and covalent alterations (phosphorylation, glycosylation).

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    Protein synthesis energy

    Protein synthesis requires energy to build a polypeptide chain, typically breaking 4 high-energy bonds per amino acid added.

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    RNA Polymerases in Eukaryotes

    Eukaryotic cells have multiple RNA polymerases, each responsible for transcribing different types of RNA.

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    Preinitiation Complex

    A group of proteins that bind to DNA before RNA polymerase, ensuring accurate positioning and initiation of transcription.

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    Regulatory Regions in a Gene

    Regions within a gene controlling gene expression, including those for basal expression (always on) and regulated expression (turned on/off).

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    Basal Transcription Complex

    A group of proteins, including transcription factors, required for basic gene expression.

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    RNA Processing

    RNA newly synthesized from DNA undergoes modifications, including intron removal and capping, to become mature mRNA.

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    Gene Expression

    The process by which a gene's information is used to create a functional product, typically a protein. It involves transcription and translation.

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    Transcription

    The synthesis of RNA from a DNA template. This is the first step in gene expression.

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    RNA Polymerase

    An enzyme that catalyzes the synthesis of RNA using a DNA template.

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    Promoter

    A DNA sequence that marks the starting point for transcription. It tells RNA polymerase where to begin.

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    TATA Box

    A DNA sequence found in promoters, typically located about 25 nucleotides upstream of the transcription start site. It helps position RNA polymerase.

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    Primary RNA Transcript

    The initial RNA molecule made during transcription. It contains both exons and introns.

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    Intron

    Non-coding sequences within a gene that are removed from the primary RNA transcript during splicing.

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    Study Notes

    Translation Overview

    • Translation is the process of synthesizing proteins using the information encoded in nucleic acids
    • It involves several stages, including:
      • Nucleotide acid structure
      • DNA replication
      • Transcription
      • Protein synthesis

    The Genetic Code

    • Proteins consist of 20 amino acids
    • mRNA, which has only 4 nucleotides, codes for these amino acids
    • A codon is a sequence of 3 nucleotides encoding an amino acid
    • There are 64 possible codon combinations, some of which code for the same amino acid

    Codons and Amino Acids

    • A table (Figure 22-3) shows the amino acid corresponding to each codon
    • The first position (5' end) determines the amino acid for the second position
    • The third position (3' end) plays a role in determining the amino acid despite some redundancy

    Reading Frames

    • mRNA sequence is read in non-overlapping triplets
    • The same sequence can be read with different meanings depending on the starting point (reading frame)

    Mutations

    • Point mutations lead to changes in the amino acid sequence
      • Nonsense mutations involve stopping the process prematurely
      • Silent mutations do not change the amino acid coded
      • Missense mutations change one amino acid to another
    • Other mutations
      • Trinucleotide repeat expansion involves the duplication of sequences causing changes in the protein (e.g., Huntington's disease)
      • Frame-shift mutations cause a change in the reading frame due to additions or deletions of nucleotides. This changes the amino acid sequence after the mutation
    • Cystic fibrosis arises from the deletion of 3 nucleotides, leading to a missing amino acid at position 508 in the CFTR protein

    Protein Synthesis Requirements

    • Amino acids
    • tRNA molecules
    • Aminoacyl-tRNA synthetases
    • mRNA
    • Ribosomes
    • Protein factors
    • ATP and GTP

    tRNA Structure and Function

    • tRNA molecules have an anticodon region that base-pairs with complementary codons on mRNA
    • Anticodon sequence determines which amino acid binds to a specific tRNA
    • Aminoacyl-tRNA synthetases attach amino acids to their corresponding tRNA molecules

    Eukaryotic Ribosomes

    • Ribosomes are sites for protein synthesis
    • They consist of rRNA and ribosomal proteins
    • They have binding sites for tRNA molecules carrying amino acids

    Peptide Bond Formation

    • Peptidyl transferase, located within the ribosome, catalyzes the formation of peptide bonds between amino acids

    Steps in Protein Translation

    • Initiation: assembly of translation components.
    • Elongation: adding amino acids to the polypeptide chain.
    • Termination: ending the process when a stop codon is reached.

    Post-translational Modifications

    • Various covalent modifications can occur after protein synthesis
      • Trimming
      • Covalent alterations (e.g., phosphorylation, glycosylation, hydroxylation, carboxylation)
      • Attachment of groups (e.g., farnesyl groups)
      • Acetylation

    Energy Requirements

    • 4 high-energy bonds are used for each amino acid added during protein synthesis.
      • Amino acid attachment to tRNA: 2 ATP bonds
      • Aminoacyl-tRNA binding to ribosome: 1 GTP bond
      • Ribosome translocation along mRNA: 1 GTP bond

    Medical Relevance

    • Antibiotics can bind to prokaryotic ribosomes, affecting translation
    • Some toxins interfere with eukaryotic translation.

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    Related Documents

    Transcription 2024 PDF
    Translation - Protein Synthesis PDF

    Description

    Explore the intricate process of protein synthesis through translation. This quiz covers nucleotide acid structures, DNA replication, transcription, and the genetic code. Test your understanding of codons, amino acids, and reading frames.

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