DNA vs. RNA: Structure and Function
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Questions and Answers

What is the primary role of RNA in protein synthesis?

  • It acts as a messenger between DNA and ribosomes. (correct)
  • It supplies energy for cellular functions.
  • It regulates gene expression.
  • It stores genetic information.

    • Which type of RNA is responsible for carrying amino acids to the ribosome?

  • rRNA
  • tRNA (correct)
  • mRNA
  • hRNA

    • What structural difference distinguishes RNA from DNA?

  • RNA contains uracil instead of thymine. (correct)
  • RNA is found exclusively in the nucleus.
  • RNA has a phosphate group.
  • RNA is composed of double-stranded nucleotides.

    • Where is DNA primarily located within a cell?

    <p>In the nucleus</p> Signup and view all the answers

    Which of the following describes the structure of mRNA?

    <p>It contains ribose sugar.</p> Signup and view all the answers

    What is the function of rRNA?

    <p>It helps in the synthesis of proteins.</p> Signup and view all the answers

    Which nitrogenous base pairs with adenine in RNA?

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

    What is a gene?

    <p>A basic unit of heredity on a chromosome.</p> Signup and view all the answers

    What is the purpose of gene expression regulation?

    <p>To ensure cells do not waste energy on unnecessary molecule production.</p> Signup and view all the answers

    What is the initial step in protein synthesis?

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

    What role does RNA polymerase play in transcription?

    <p>It binds to DNA and synthesizes mRNA.</p> Signup and view all the answers

    Which of the following statements about exons is true?

    <p>They code for amino acids and are joined together.</p> Signup and view all the answers

    During which process does mRNA carry genetic information from the nucleus to the ribosome?

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

    Which statement best describes the nature of DNA in the context of protein synthesis?

    <p>DNA is double-stranded and too large to exit the nucleus.</p> Signup and view all the answers

    Which of the following would represent an example of cyclical gene expression?

    <p>Temporary expression of estrogen.</p> Signup and view all the answers

    What are introns primarily responsible for?

    <p>Regulating gene expression</p> Signup and view all the answers

    How are amino acids essential to protein synthesis?

    <p>They are combined in various sequences to form proteins.</p> Signup and view all the answers

    During mRNA processing, what occurs to introns?

    <p>They are cut out before mRNA exits the nucleus</p> Signup and view all the answers

    What is the first step of translation?

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

    What does a codon represent?

    <p>A triplet of nucleotides that codes for a specific amino acid</p> Signup and view all the answers

    How does tRNA contribute to translation?

    <p>It joins amino acids based on mRNA codons</p> Signup and view all the answers

    What happens during elongation in the translation process?

    <p>A tRNA transfers an amino acid to the next tRNA</p> Signup and view all the answers

    What is the function of rRNA in translation?

    <p>To form the ribosome and facilitate mRNA reading</p> Signup and view all the answers

    What ultimately signals the completion of a protein during translation?

    <p>Reaching a stop codon</p> Signup and view all the answers

    What type of mutation occurs when one base is substituted for another?

    <p>Substitution mutation</p> Signup and view all the answers

    What is the result of a nonsense mutation?

    <p>Early termination of the polypeptide chain</p> Signup and view all the answers

    Which type of mutation is typically caused by the removal of a base from the DNA sequence?

    <p>Deletion mutation</p> Signup and view all the answers

    What is a potential outcome of a frameshift mutation?

    <p>The reading frame shifts, altering all subsequent amino acids</p> Signup and view all the answers

    Which of the following is NOT a cause of gene mutations?

    <p>Genetic inheritance</p> Signup and view all the answers

    What type of effect does a silent mutation have on the proteins being synthesized?

    <p>It has no effect on the protein produced</p> Signup and view all the answers

    What is the approximate frequency of gene mutations occurring during DNA replication?

    <p>1 in every 100,000,000 bases</p> Signup and view all the answers

    Which of the following describes a missense mutation?

    <p>It affects one amino acid in the protein chain</p> Signup and view all the answers

    Study Notes

    DNA vs. RNA

    • DNA is a double helix composed of nucleotides with a deoxyribose sugar, phosphate group, and nitrogenous bases (Adenine, Thymine, Cytosine, Guanine).
    • DNA resides in the nucleus as it is too large to leave.
    • DNA codes for genes which make proteins.
    • RNA acts as a messenger between DNA and ribosomes to build proteins from amino acids.
    • RNA differs from DNA in its sugar (ribose vs. deoxyribose), number of strands (single vs. double), location (inside and outside the nucleus vs. only inside), and base pairing (uracil instead of thymine).

    Types of RNA

    • mRNA (messenger RNA): Copies the code from DNA in the nucleus and takes it to the ribosome.
    • tRNA (transfer RNA): Transfers specific amino acids to the ribosome to match with mRNA and build a protein.
    • rRNA (ribosomal RNA): Forms ribosomes along with proteins.

    Gene Expression

    • Gene expression refers to the active production of a protein from a gene.
    • Not all genes are expressed simultaneously.
    • Some genes are rarely expressed (e.g., adrenaline), some are constantly expressed (e.g., hair growth), and some are cyclically expressed (e.g., estrogen).
    • Gene expression (protein synthesis) is essential for cell differentiation and function.

    Protein Synthesis

    • Protein synthesis is a two-stage process for producing proteins from DNA.
    • Also known as gene expression or the central dogma.
    • The two steps include transcription and translation.

    Transcription

    • Transfers information from DNA to mRNA.
    • Necessary because DNA is too large to leave the nucleus, while RNA can.
    • RNA polymerase binds to DNA, unzips it, and uses one strand as a template to create a single-stranded mRNA.

    Regulation in Transcription

    • mRNA is processed/edited before leaving the nucleus to remove non-coding regions (introns).
    • Exons (coding regions) are spliced together to form the final mRNA that leaves the nucleus.

    Translation

    • Decodes mRNA into a protein.
    • tRNA transfers specific amino acids to the ribosome based on mRNA codons.
    • Amino acids are joined together to form a protein.

    Codons

    • A series of three mRNA bases that code for a specific amino acid.
    • Start codon: AUG (codes for methionine)
    • Stop codons: UAG, UAA, UGA

    Role of tRNA in Translation

    • tRNA has an anticodon that is complementary to the codon in mRNA.
    • tRNA delivers the matching amino acid to the ribosome.

    Steps of Translation

    • Initiation: Ribosome assembles around mRNA, with the first tRNA attaching to the start codon.
    • Elongation: tRNAs transfer amino acids to the tRNA of the next codon.
    • Termination: When the stop codon is reached, the ribosome releases the polypeptide.

    Gene Mutations

    • Errors during DNA replication that change a single gene.
    • Rare occurrence (1 in 100,000,000 bases).
    • Can have a major effect on the protein being made.

    Point Mutations

    • Occur at a single point (change to one base).
    • Types include substitution, deletion, and insertion.

    Substitution Mutations

    • One base is changed for another.
    • Can be silent, missense, or nonsense.

    Silent Mutations

    • Do not affect the protein being made.

    Missense Mutations

    • Affect one amino acid in the protein chain, with varying effects on the protein's function.

    Nonsense Mutations

    • Cause an early stop codon, terminating the polypeptide chain sequence prematurely.
    • Severely affect the protein being made.

    Deletion/Insertion Mutations

    • Base removed or inserted from the DNA sequence.
    • Cause a frameshift mutation.

    Frameshift Mutations

    • Shift the reading frame of the genetic message.
    • Can change every amino acid following the mutation point.
    • May render the protein non-functional.

    Causes of Gene Mutations

    • Spontaneous occurrence during cell replication.
    • Environmental agents (mutagenic agents): UV light, radiation.
    • Cancer-causing agents (carcinogens): Chemicals (cigarette smoke), viruses (HPV).

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    Unit 4 Protein Synthesis Notes PDF

    Description

    This quiz explores the differences between DNA and RNA, including their structure, function, and types. Learn about the roles each molecule plays in gene expression and protein synthesis. Ideal for students studying molecular biology.

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