Lecture 4: DNA Replication
39 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the minimum number of polypeptides required for DNA polymerase III functional activity?

  • One
  • Two
  • Five
  • Three (correct)

    • Who discovered DNA polymerase I in 1958?

  • Arthur Kornberg (correct)
  • Francis Crick
  • James Watson
  • Rosalind Franklin

    • What is the role of DNA ligase in DNA replication?

  • Forming phosphodiester bonds (correct)
  • Unwinding of parental DNA
  • Synthesizing RNA primers
  • Initiating DNA synthesis

    • What is the approximate length of Okazaki fragments in prokaryotic cells?

    <p>2000 nucleotides</p> Signup and view all the answers

    Which DNA polymerase is involved in the replication of mitochondrial DNA?

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

    What is the primary function of DNA polymerase delta?

    <p>Completing replication on leading and lagging strands</p> Signup and view all the answers

    Which DNA polymerase is responsible for initiating nuclear DNA synthesis?

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

    What is the primary function of DNA polymerase beta?

    <p>Repairing DNA damage</p> Signup and view all the answers

    What is the key characteristic of semi-conservative replication?

    <p>Each of the progeny DNA molecules conserves half of the original DNA molecule.</p> Signup and view all the answers

    What is the main problem with conservative and dispersive replication?

    <p>They do not immediately suggest a mechanism for copying the information in the sequence of bases.</p> Signup and view all the answers

    What is the function of CsCl2 equilibrium density gradient centrifugation in the Meselson and Stahl experiment?

    <p>To separate DNA molecules based on their density.</p> Signup and view all the answers

    What is the difference between 14N and 15N ammonium salts?

    <p>The isotope of nitrogen.</p> Signup and view all the answers

    What is the significance of the Watson and Crick DNA model?

    <p>It suggested how genetic information might be replicated.</p> Signup and view all the answers

    What is the characteristic of DNA from E. coli cells grown with 15N ammonium salts?

    <p>It has a higher density than DNA grown in 'normal' (14N) ammonium salts.</p> Signup and view all the answers

    What is the purpose of the Meselson and Stahl experiment?

    <p>To determine the mechanism of DNA replication.</p> Signup and view all the answers

    What is the characteristic of prokaryotic organisms?

    <p>They lack a true membrane-bound nucleus and cellular organelles.</p> Signup and view all the answers

    Which DNA polymerase appears to take part in nuclear replication of both the leading and the lagging strands?

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

    What type of replication occurs in eukaryotes?

    <p>Semi-conservative replication</p> Signup and view all the answers

    What is the function of replication licensing factor (RLF)?

    <p>To bind to the DNA next to each origin before each replication cycle</p> Signup and view all the answers

    How many replication origins are estimated to be in a dividing human somatic cell?

    <p>10,000-100,000</p> Signup and view all the answers

    What is the term for the bulges where the DNA is in the process of division?

    <p>Replication bubbles</p> Signup and view all the answers

    How does DNA replication occur in eukaryotes?

    <p>Bi-directional</p> Signup and view all the answers

    What is the function of other DNA polymerases?

    <p>To allow replication to bypass damaged DNA or play a role in DNA repair</p> Signup and view all the answers

    How are the new strands synthesized in eukaryotic DNA replication?

    <p>One strand is synthesized continuously and the other in fragments</p> Signup and view all the answers

    What determines the migration position of DNA in centrifugation?

    <p>Density of DNA</p> Signup and view all the answers

    What was the result of switching E.coli to 14N media after growing them in 15N salts?

    <p>A single band of intermediate density was observed</p> Signup and view all the answers

    What is the mode of DNA replication supported by the results of Meselson and Stahl's experiment?

    <p>Semi-conservative</p> Signup and view all the answers

    What is the function of DNA polymerase in DNA replication?

    <p>Deoxynucleotide polymerization</p> Signup and view all the answers

    What is the role of RNA primers in DNA replication?

    <p>To initiate DNA synthesis</p> Signup and view all the answers

    What is the function of helicase in DNA replication?

    <p>To unwind DNA</p> Signup and view all the answers

    What is the name of the complex that constitutes helicase and primase?

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

    What is the name of the protein that melts duplex DNA in the oriC region?

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

    What is the purpose of DNA replication?

    <p>To create an identical copy of the DNA for each descendant cell</p> Signup and view all the answers

    What is the base pairing rule in DNA replication?

    <p>A pairs with T and G pairs with C</p> Signup and view all the answers

    What happens to the two DNA strands in the first stage of replication?

    <p>They are separated</p> Signup and view all the answers

    What is the replication fork?

    <p>The zone of DNA where the strands are separated</p> Signup and view all the answers

    What is the result of DNA replication?

    <p>Two double-stranded DNA molecules with identical sequences</p> Signup and view all the answers

    How many nucleotides per second are synthesized in E. coli?

    <p>1,000 nucleotides per second</p> Signup and view all the answers

    What is the role of the replisome?

    <p>To synthesize new DNA strands</p> Signup and view all the answers

    Study Notes

    DNA Replication

    • DNA replication is a two-stage process that occurs at the replication fork
    • The first stage separates the two DNA strands of the parental DNA molecule
    • The second stage builds two new strands using each of the two original strands as templates
    • Base pairing occurs between A and T, and between G and C
    • Each of the separated parental strands of DNA serves as a template strand for the synthesis of a new complementary strand
    • Synthesis of both new strands of DNA occurs at the replication fork that moves along the parental molecule

    Semi-Conservative Replication

    • There are three possible strategies for replication of the double helix: semi-conservative, conservative, and dispersive
    • Semi-conservative replication is the most satisfactory mechanism, as it allows for copying the information in the sequence of bases
    • In semi-conservative replication, each of the progeny conserves half of the original DNA molecule
    • One of the two “daughter” double helices consists entirely of original DNA strands, while the other helix consists of two newly synthesized strands

    Meselson and Stahl Experiment

    • In 1958, Meselson and Stahl performed an experiment to determine the mode of replication
    • They grew E. coli in 15N ammonium salts, which resulted in DNA with a higher density than normal DNA
    • When they switched the media to 14N salts, the DNA density changed
    • After one round of replication, a single band of intermediate density was observed
    • After a second round of replication, two bands were present in approximately equimolar amounts
    • The results were consistent with a semi-conservative mode of replication for DNA

    Mechanism of DNA Replication

    • The process involves deoxyribonucleotide precursors synthesis, deoxynucleotide polymerization, and enzymes and proteins such as DNA polymerase, primase, and ligase
    • RNA primers are also involved in the process
    • The steps in E. coli DNA synthesis include:
      • dnaA protein melts duplex in oriC region
      • dnaB (helicase) and dnaC protein bind to replication fork
      • Single-strand binding protein (ssb protein) binds to separated strands of DNA
      • Primase complexes with helicase and creates RNA primers
      • DNA pol III holoenzyme extends the RNA primer on the leading strand

    Prokaryotic and Eukaryotic Replication

    • Prokaryotic replication occurs in bacteria, while eukaryotic replication occurs in eukaryotic cells such as plants and animals
    • Eukaryotic chromosomes are longer and have multiple replication origins scattered along each chromosome
    • Replication is bi-directional, with a pair of replication forks starting at each origin of replication
    • Eukaryotic DNA replication involves multiple DNA polymerases, including alpha, delta, gamma, and epsilon

    Replication Licensing Factor (RLF)

    • RLF is a protein complex that binds to the DNA next to each origin before each replication cycle
    • RLF is displaced during replication and ensures that each origin initiates once and once only during each replication cycle

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz covers the process of DNA replication, including the two-stage process that occurs at the replication fork, and the separation of the two DNA strands of the parental DNA molecule.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser