DNA Structure & Replication Quiz
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Questions and Answers

What is the role of DNA polymerase in DNA replication?

  • Creates RNA primers to start replication
  • Unwinds the DNA helix
  • Adds complementary nucleotides to the growing strand (correct)
  • Seals the gaps between Okazaki fragments

    • During transcription, what is the role of the promoter region?

  • It is the region where the DNA helix unwinds.
  • It is the site where RNA polymerase binds to initiate transcription. (correct)
  • It is the region where Okazaki fragments are joined together.
  • It is the site where the mRNA is translated into protein.

    • What is the difference between a missense mutation and a nonsense mutation?

  • A missense mutation is caused by an insertion or deletion, while a nonsense mutation is caused by a substitution
  • A missense mutation changes an amino acid in the protein sequence, while a nonsense mutation changes a codon to a stop codon. (correct)
  • A missense mutation is a frameshift mutation, while a nonsense mutation is a point mutation.
  • A missense mutation changes a codon to a stop codon, while a nonsense mutation changes a codon to a different amino acid.

    • What is the function of tRNA in translation?

    <p>It brings the corresponding amino acid to the ribosome based on the mRNA codon. (C)</p> Signup and view all the answers

    Which of the following scientists is credited with discovering the double-helix structure of DNA?

    <p>James Watson and Francis Crick (D)</p> Signup and view all the answers

    What is the importance of the 5' to 3' directionality in DNA replication?

    <p>DNA polymerase can only add nucleotides to the 3' end of a growing strand. (C)</p> Signup and view all the answers

    Which of the following is NOT a type of chromosomal mutation?

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

    What is the function of the lac operon in bacteria?

    <p>To regulate the expression of genes involved in lactose metabolism. (B)</p> Signup and view all the answers

    Which of the following is NOT an example of an epigenetic marker?

    <p>Gene deletion (C)</p> Signup and view all the answers

    What type of transcription factor represses gene expression?

    <p>Negative transcription factor (A)</p> Signup and view all the answers

    What is the function of a frameshift mutation?

    <p>It shifts the reading frame of the codons, leading to a different protein sequence. (B)</p> Signup and view all the answers

    What type of mutation results in a change in the amino acid sequence of a protein?

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

    Which of the following is NOT a type of RNA involved in gene expression regulation?

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

    How can mutations contribute to genetic diversity within a population?

    <p>They introduce variations that can be acted upon by natural selection. (D)</p> Signup and view all the answers

    What is the role of RNA processing in eukaryotes?

    <p>It adds a cap and tail to the mRNA, and removes non-coding regions called introns. (D)</p> Signup and view all the answers

    What is the difference between the leading strand and the lagging strand in DNA replication?

    <p>The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously in fragments. (C)</p> Signup and view all the answers

    What mechanism leads to deleterious changes in protein structure due to a shift in the reading frame of mRNA?

    <p>Frameshift Mutation (C)</p> Signup and view all the answers

    Which enzyme is primarily responsible for creating RNA primers during DNA replication?

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

    In what way do positive transcription factors affect gene expression?

    <p>They enhance or activate gene expression. (A)</p> Signup and view all the answers

    What is the primary role of RNA polymerase during transcription?

    <p>To synthesize RNA from a DNA template. (C)</p> Signup and view all the answers

    What is a characteristic feature of chromosomal duplications?

    <p>A segment of a chromosome is repeated. (B)</p> Signup and view all the answers

    Which codon signals the termination of translation?

    <p>UAA (C)</p> Signup and view all the answers

    Which of the following accurately describes a nonsense mutation?

    <p>It introduces a premature stop codon. (B)</p> Signup and view all the answers

    What defines an operon in molecular biology?

    <p>A group of genes regulated together under a single promoter. (D)</p> Signup and view all the answers

    Which type of RNA is specifically involved in regulating gene expression and preventing translation?

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

    What is the main function of histone modifications in gene expression?

    <p>To condense or relax chromatin structure. (D)</p> Signup and view all the answers

    What is the function of ligase during DNA replication?

    <p>To seal gaps between Okazaki fragments. (D)</p> Signup and view all the answers

    In which cellular compartment does transcription occur in eukaryotes?

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

    What does DNA methylation typically do to gene expression?

    <p>Represses gene expression. (D)</p> Signup and view all the answers

    Flashcards

    Nucleotide

    Building block of DNA, composed of sugar, phosphate, and nitrogenous base.

    Chargaff's Rule

    A=T and C=G; rules for complementary base pairing in DNA.

    Antiparallel DNA

    Strands of DNA run in opposite directions: 5' to 3' and 3' to 5'.

    DNA Replication Enzymes

    Key enzymes include helicase, DNA polymerase, ligase, and primase.

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    Leading Strand

    The continuously synthesized DNA strand in the 5' to 3' direction.

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    Lagging Strand

    Synthesized discontinuously in fragments (Okazaki fragments).

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    Transcription

    Process of creating mRNA from DNA in the nucleus using RNA polymerase.

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    Translation

    Process where ribosomes read mRNA codons to assemble amino acids into proteins.

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    Codons

    Sets of three mRNA bases that correspond to specific amino acids.

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    Start Codon

    AUG signals the beginning of translation and codes for Methionine.

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    Stop Codons

    UAA, UAG, UGA signal the end of translation.

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    Point Mutation

    Change in a single nucleotide base; includes substitutions, silent, missense, and nonsense mutations.

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    Chromosomal Mutations

    Alterations involving larger sections of DNA, including deletions, duplications, inversions, and translocations.

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    Epigenetics

    Study of changes in gene expression not caused by changes in DNA sequence.

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    Gene Expression Regulation

    Control of which proteins are made and how much; crucial for cellular function.

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    RNA Polymerase

    Enzyme that synthesizes mRNA from a DNA template during transcription.

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    RNA Processing

    Modification of mRNA in eukaryotes, including splicing and adding a cap and tail.

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    tRNA

    Transfer RNA that brings amino acids to the ribosome during translation.

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    Peptide Bonds

    Chemical bonds formed between amino acids during protein synthesis.

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    Positive Transcription Factors

    Proteins that enhance or activate gene expression.

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    Negative Transcription Factors

    Proteins that repress or inhibit gene expression.

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    Operon

    A group of genes regulated together under a single promoter.

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    miRNA

    MicroRNA that regulates gene expression by binding to mRNA.

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    Histone Modification

    Chemical changes to histone proteins affecting gene accessibility.

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    Frameshift Mutation

    Mutation caused by insertions or deletions that shift the reading frame of codons.

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    Silent Mutation

    Point mutation that does not change the amino acid sequence.

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    Nonsense Mutation

    Point mutation that converts an amino acid codon into a stop codon.

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    Methylation

    Addition of methyl groups to DNA, usually repressing gene expression.

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    Chromosomal Deletion

    Loss of a segment of a chromosome.

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    Study Notes

    DNA Structure & Replication

    • Nucleotide: Composed of a sugar (deoxyribose), a phosphate group, and a nitrogenous base (A, T, C, G).
    • Chargaff's Rule: A = T and C = G (complementary base pairing).
    • Antiparallel: The two DNA strands run in opposite directions (5' to 3' vs 3' to 5').
    • Watson and Crick: Discovered the double-helix structure.
    • Rosalind Franklin: Contributed to the structure via X-ray diffraction images.
    • Erwin Chargaff: Discovered base pairing rules (A = T, C = G).
    • Helicase: Unwinds the DNA helix.
    • DNA Polymerase: Adds complementary nucleotides to the growing strand.
    • Ligase: Seals the gaps between Okazaki fragments.
    • Primase: Creates RNA primers to start replication.
    • Leading Strand: Synthesized continuously in the 5' to 3' direction.
    • Lagging Strand: Synthesized discontinuously in fragments (Okazaki fragments).
    • Okazaki Fragments: Short segments of DNA synthesized on the lagging strand.

    Protein Synthesis

    Transcription

    • Location: Occurs in the nucleus (eukaryotes).
    • Process:
      • RNA Polymerase binds to DNA at the promoter region.
      • RNA polymerase creates an mRNA strand using the DNA template.
      • mRNA synthesis occurs from 5' to 3'.
      • In eukaryotes, mRNA is processed (splicing, capping, and tailing).

    Translation

    • Location: Occurs in the ribosome (cytoplasm).
    • Process:
      • mRNA is read in sets of three bases (codons).
      • tRNA brings the corresponding amino acids to the ribosome.
      • Ribosome forms peptide bonds to create a polypeptide chain.
      • Codon Chart/Wheel: Used to match mRNA codons to amino acids.
      • START Codon: AUG, signals the beginning of translation.
      • STOP Codons: UAA, UAG, UGA, signal the end of translation.

    Gene Expression

    • Importance: Regulates which proteins are made, when, and in what amounts.
    • Transcription Factors:
      • Positive: Activate/enhance gene expression.
      • Negative: Repress gene expression.
      • Binding Sites: Bind to specific regions on the promoter of a gene.
    • Interfering RNA (RNAi):
      • Types: miRNA and siRNA.
      • Function: Regulate gene expression by binding to mRNA, preventing translation, or degrading mRNA.
    • Operons:
      • Definition: Genes regulated together.
      • Example: Lac Operon (bacteria).
    • Epigenetics: Study of changes in gene expression without changing DNA sequence.
      • Examples: DNA Methylation (suppresses gene expression via methyl group addition to DNA) and Histone Modification (alters chromatin condensation, affecting gene accessibility).

    Variation & Mutations

    • Mutations: Changes in DNA sequences.
    • Frameshift Mutations: Caused by insertions or deletions, shifting the reading frame of codons.
    • Point Mutations: Changes in a single nucleotide.
      • Substitution: One base is replaced by another.
        • Silent Mutation: No change in the protein sequence.
        • Missense Mutation: Changes one amino acid.
        • Nonsense Mutation: Changes a codon to a stop codon, creating a truncated protein.
    • Impact on Fitness: Mutations can be beneficial, harmful, or neutral for survival and reproduction.
    • Chromosomal Mutations:
      • Deletions: Loss of a chromosome segment.
      • Duplications: Repetition of a chromosome segment.
      • Inversions: Reversal of a chromosome segment.
      • Translocations: Exchange of segments between non-homologous chromosomes.
    • Mutations and Population Variation: Mutations contribute to genetic diversity. Natural selection can act upon these variations.

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    Unit 4 Honors Study Guide: Protein Synthesis & Mutations PDF

    Description

    Test your knowledge on the structure and replication of DNA. This quiz covers essential concepts such as nucleotide composition, Chargaff's rule, and the contributions of scientists like Watson, Crick, and Franklin. Enhance your understanding of the processes involved in DNA replication including the roles of various enzymes.

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