DNA Structure and Replication Quiz
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Questions and Answers

What components make up a nucleotide in DNA?

  • A phosphate group, a ribose sugar, and a nitrogen base
  • A deoxyribose sugar, a nitrogen base, and an amino acid
  • A sugar, a nitrogen base, and a hydroxyl group
  • A sugar, a nitrogen base, and a phosphate group (correct)

    • Which pair of nucleotides are classified as purines?

  • Adenine and Guanine (correct)
  • Guanine and Cytosine
  • Adenine and Thymine
  • Thymine and Cytosine

    • What is the function of a phosphodiester bond in DNA structure?

  • To provide structural stability to ribose sugars
  • To form hydrogen bonds between base pairs
  • To connect nucleotides within a single strand (correct)
  • To link different strands of DNA together

    • How do adenine (A) and thymine (T) bond in DNA?

    <p>By hydrogen bonding</p> Signup and view all the answers

    In DNA, which of the following statements about the nitrogenous bases is correct?

    <p>Adenine and Guanine are both purines.</p> Signup and view all the answers

    What determines the difference among the four types of nucleotides in DNA?

    <p>The nitrogenous base</p> Signup and view all the answers

    In terms of structure, which statement about purines and pyrimidines is true?

    <p>Pyrimidines have a single ring structure.</p> Signup and view all the answers

    What is the significance of semi-conservative replication in DNA replication?

    <p>Each new DNA molecule contains one old and one new strand.</p> Signup and view all the answers

    Which statement correctly describes the orientation of DNA strands?

    <p>One strand runs 5’ to 3’ while the other runs 3’ to 5’.</p> Signup and view all the answers

    During which phase does DNA replication occur in eukaryotes?

    <p>S phase</p> Signup and view all the answers

    What is the direction of DNA synthesis during replication?

    <p>5’-3’ direction</p> Signup and view all the answers

    What role does helicase play in DNA replication?

    <p>It unwinds the double-helical structure of DNA.</p> Signup and view all the answers

    What is primarily required for the initiation of DNA replication?

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

    Which process describes the accurate transmission of genetic material to daughter cells during cell division?

    <p>Mitosis and cytokinesis</p> Signup and view all the answers

    Which enzyme activity is involved in stabilizing the unwound DNA strands during replication?

    <p>Single-strand binding protein</p> Signup and view all the answers

    What is the process called when daughter chromosomes are separated into two daughter cells?

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

    What is the primary role of primase in DNA replication?

    <p>It adds ribonucleoside triphosphates to synthesize an RNA primer.</p> Signup and view all the answers

    In which direction does DNA polymerase add nucleotides during elongation?

    <p>5' to 3'</p> Signup and view all the answers

    What function does exonuclease serve in DNA replication?

    <p>It removes nucleotides from the end of a DNA strand.</p> Signup and view all the answers

    Which of the following describes the role of ligase in DNA replication?

    <p>It joins ends of single DNA strands by making new phosphate bonds.</p> Signup and view all the answers

    What characteristic differentiates RNA from DNA?

    <p>RNA uses ribose instead of deoxyribose.</p> Signup and view all the answers

    Why is a template necessary for DNA polymerase function?

    <p>To ensure proper nucleotide sequence.</p> Signup and view all the answers

    What unique feature of eukaryotic DNA replication is highlighted?

    <p>There are multiple origins of replication.</p> Signup and view all the answers

    How does the proofreading activity of DNA polymerase benefit DNA replication?

    <p>It ensures that incorrect nucleotides are removed and replaced.</p> Signup and view all the answers

    What is the role of telomerase in DNA replication?

    <p>To add short DNA repeats to the ends of linear chromosomes.</p> Signup and view all the answers

    What occurs at the 5' end of each daughter strand after RNA primer removal?

    <p>A gap is left due to the absence of a preceding 3'-OH.</p> Signup and view all the answers

    What is primarily responsible for adding nucleotides to the growing daughter strand during DNA replication?

    <p>Polymerase activity of ε DNA polymerase.</p> Signup and view all the answers

    Which sequence represents the highly conserved telomeric repeats found in humans?

    <p>TTAGGG/AATCCC.</p> Signup and view all the answers

    Which enzyme relaxes supercoiling that occurs during DNA replication?

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

    Study Notes

    DNA Structure

    • DNA is a nucleic acid made of two polynucleotides.
    • Each polynucleotide consists of nucleotides, which are made of a deoxyribose sugar, a phosphate group, and a nitrogenous base.
    • There are four different types of nucleotides in DNA: adenine (A), guanine (G), cytosine (C), and thymine (T).
    • Adenine and guanine are purines, which have two rings.
    • Cytosine and thymine are pyrimidines, which have one ring.
    • Adenine pairs with thymine through hydrogen bonding.
    • Guanine pairs with cytosine through hydrogen bonding.
    • The two strands of DNA run in opposite directions (antiparallel) with a 5' end and a 3' end.
    • The 5' end has a free phosphate group, and the 3' end has a free hydroxyl group.
    • Nucleotides are linked together by phosphodiester bonds between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of the next.

    DNA Replication

    • DNA replication must occur before cell division to ensure each daughter cell receives a complete set of genes.
    • DNA replication is semiconservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.
    • DNA replication proceeds in a 5' to 3' direction.
    • DNA replication is bidirectional, with replication forks moving in opposite directions away from the origin of replication.
    • There are multiple origins of replication in eukaryotes but only one in prokaryotes.
    • Replication of the entire mammalian genome takes approximately 8 hours.

    Enzymes Involved in DNA Replication

    • Helicase: unwinds the double helix.
    • Single-strand binding proteins (SSBPs): stabilize the single-stranded DNA to keep it unwound.
    • Primase: synthesizes RNA primers, which are required by DNA polymerase to start replication.
    • DNA polymerase: adds nucleotides to the growing DNA strand in a 5' to 3' direction, using the parental strand as a template. It also has proofreading activity.
    • Exonuclease: removes nucleotides from the end of a DNA strand in either the 5' to 3' or 3' to 5' direction. It also removes the RNA primers.
    • Ligase: joins fragments of DNA together.
    • Telomerase: adds short DNA repeats to the ends of linear chromosomes to prevent loss of genetic information.
    • Gyrase: relaxes supercoils that form during replication.

    Steps of DNA Replication

    • Initiation: unwinding of the DNA helix at the origin of replication.
    • Elongation: synthesis of new DNA strands.
    • Termination: completion of replication and separation of the two daughter DNA molecules.

    Leading and Lagging Strands

    • Leading strand: synthesized continuously in the 5' to 3' direction.
    • Lagging strand: synthesized discontinuously in short fragments called Okazaki fragments.

    Telomeres

    • Telomeres are G:C rich repeats found at the ends of linear chromosomes.
    • Telomeres are non-coding but critical for maintaining DNA integrity.
    • Telomerase adds short DNA repeats to the ends of chromosomes, preventing the loss of genetic information.

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    Description

    Test your knowledge on the structure and replication of DNA. This quiz covers the key components of DNA, including nucleotides, their pairing, and the process of DNA replication. Perfect for students studying molecular biology.

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