DNA Replication and Structure Quiz
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Questions and Answers

The leading and the lagging strands differ in that?

  • The lagging strand is synthesized in the same direction as the movement of the replication fork.
  • The leading strand is synthesized in the opposite direction of the replication fork.
  • The lagging strand is synthesized in opposite direction of the movement of the replication fork. (correct)
  • The leading strand is synthesized in the same direction as the movement of the replication fork. (correct)

    • What does a space probe return with?

  • A sample of soil
  • A culture of a microorganism found on a distant planet. (correct)
  • Data about atmospheric compositions
  • None of the above

    • In the late 1950s, what did Meselson and Stahl grow in a medium containing 'heavy' nitrogen (15N)?

  • S. pneumoniae
  • A virus
  • Yeast
  • E. coli bacteria (correct)

    • What type of genetic material does the tobacco mosaic virus have?

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

    What forms during DNA replication due to a transient exposure to radioactive nucleotides?

    <p>Okazaki fragments and RNA primers.</p> Signup and view all the answers

    What did biologists know about the nucleus for a couple of decades?

    <p>It contained DNA and proteins.</p> Signup and view all the answers

    The DNA double helix has a uniform diameter because ___, which have two rings, always pairs with ___, which have one ring.

    <p>purines; pyrimidines</p> Signup and view all the answers

    What must be done to the living cells in the modified Hershey and Chase experiment?

    <p>Amino acids must be distinguished from proteins.</p> Signup and view all the answers

    Which enzyme catalyzes the elongation of a DNA strand?

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

    What is the role of DNA ligase during DNA replication?

    <p>Join Okazaki fragments together</p> Signup and view all the answers

    What do the descendants of heat-killed, phosphorescent bacteria reveal?

    <p>They are also phosphorescent.</p> Signup and view all the answers

    Which proteins help to hold the DNA strands apart during replication?

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

    What occurs in a eukaryotic cell lacking telomerase?

    <p>A reduction in chromosome lengths.</p> Signup and view all the answers

    Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?

    <p>Because DNA polymerase can assemble DNA only in the 5' to 3' direction.</p> Signup and view all the answers

    In a nucleotide, the nitrogenous base is attached to the sugar's ____

    <p>1'</p> Signup and view all the answers

    Hershey and Chase used ___ to radioactively label the T2 phage's proteins.

    <p>35S</p> Signup and view all the answers

    The spontaneous loss of amino groups from adenine results in what?

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

    What does a biochemist isolate and purify for DNA replication?

    <p>DNA ligase</p> Signup and view all the answers

    What happens to a eukaryotic cell lacking active telomerase?

    <p>Experiences gradual reduction of chromosome length with each replication cycle.</p> Signup and view all the answers

    In his work with pneumonia-causing bacteria and mice, what did Griffin find?

    <p>Some substance from pathogenic cells were transferred to nonpathogenic cells.</p> Signup and view all the answers

    Why does a new DNA strand elongate only in the 5' to 3' direction?

    <p>Because DNA polymerase can only add nucleotides to the free 3' end.</p> Signup and view all the answers

    What synthesizes short segments of RNA?

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

    Why are individuals with xerodermia pigmentosum hypersensitive to sunlight?

    <p>Because their cells have an impaired ability to repair thymine dimers.</p> Signup and view all the answers

    What happens when phage with labeled proteins or DNA infects bacteria?

    <p>The genetic material is introduced into the bacterial cells.</p> Signup and view all the answers

    Which of the following statements does not apply to the Watson and Crick model of DNA?

    <p>The two strands of the helix are held together by covalent bonds.</p> Signup and view all the answers

    What did Chargaff's analysis of the base composition of DNA show?

    <p>Both A and C</p> Signup and view all the answers

    What does replicating the lagging strand of DNA involve?

    <p>All of the above</p> Signup and view all the answers

    What is the function of DNA polymerase?

    <p>To add nucleotides to the end of a growing DNA strand.</p> Signup and view all the answers

    In an analysis of the nucleotide composition of DNA, which of the following is true?

    <p>Both C and D</p> Signup and view all the answers

    What is the difference between ATP and the nucleotides triphosphates used during DNA synthesis?

    <p>Nucleotide triphosphates have deoxyribose sugar.</p> Signup and view all the answers

    Study Notes

    DNA Replication and Structure

    • Leading strand synthesizes in the same direction as the replication fork; lagging strand synthesized in the opposite direction.
    • DNA double helix maintains a uniform diameter due to pairing of purines (two rings) with pyrimidines (one ring).
    • DNA polymerase catalyzes the elongation of the DNA strand in the 5' to 3' direction.
    • New DNA strand forms in short segments (Okazaki fragments) on the lagging strand because DNA polymerase only adds nucleotides to the free 3' end.
    • DNA ligase joins Okazaki fragments together during replication, ensuring a continuous strand.

    Molecular Components and Enzymes

    • Tobacco mosaic virus contains RNA as its genetic material instead of DNA.
    • Single-strand binding proteins hold DNA strands apart during replication to prevent re-annealing.
    • Nucleotides consist of a sugar, phosphate group, and nitrogenous base; the base is attached to the sugar’s 1' carbon and the phosphate group to the 5' carbon.

    Experiments and Findings

    • Hershey and Chase used radioactive sulfur-35 to label proteins in the T2 phage, highlighting the genetic material's role.
    • Meselson and Stahl's experiment differentiated DNA using heavy nitrogen (15N) versus light nitrogen (14N) to confirm semi-conservative replication.
    • Griffith's experiments demonstrated that a non-pathogenic strain of bacteria could become pathogenic when mixed with heat-killed pathogenic strains.

    Effects of Genetic Disorders

    • Individuals with xeroderma pigmentosum have impaired ability to repair thymine dimers, causing hypersensitivity to sunlight.
    • A eukaryotic cell without telomerase gradually reduces chromosome length after each replication cycle.

    Key Principles and Observations

    • Chargaff’s rules indicate that the amounts of adenine equal thymine and cytosine equal guanine in DNA.
    • Certain amino acids contain nitrogen atoms, posing challenges in distinguishing between DNA and protein in experimental setups.

    Summary of DNA Synthesis and Composition

    • Differences between ATP and nucleotides used in DNA synthesis involve sugar types: deoxyribose in nucleotides and ribose in ATP.
    • Nucleotides are essential for DNA replication; DNA polymerase functions to add these nucleotides to the growing DNA strand.

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    Description

    Test your knowledge on DNA replication and the molecular components involved! This quiz covers key concepts such as the roles of leading and lagging strands, the function of DNA polymerase, and the importance of enzymes in the process. Perfect for students studying molecular biology.

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