Biology Lab: DNA Structure and Replication
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Questions and Answers

What are the two types of nitrogen-containing bases found in DNA?

  • Purines and Pyrimidines (correct)
  • Purines and Pyrazines
  • Amino acids and Peptides
  • Ketones and Aldehydes
  • What is the main function of the phosphate group in a nucleotide?

  • To bind with the nitrogen-containing bases
  • To provide energy for DNA replication
  • To stabilize the double helix structure
  • To form the backbone of the DNA molecule (correct)
  • What is the direction of the nucleotide strands in a DNA molecule?

  • Parallel and complementary
  • Antiparallel and identical
  • Parallel and identical
  • Antiparallel and complementary (correct)
  • What is the direction of strand elongation during DNA replication?

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

    What type of bonds hold the nucleotide strands together in a DNA molecule?

    <p>Hydrogen bonds</p> Signup and view all the answers

    What is the name of the model that describes the structure of DNA as a double helix?

    <p>Watson-Crick Model</p> Signup and view all the answers

    Which of the following is NOT a basic requirement for DNA replication?

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

    What is the function of primase during DNA replication?

    <p>To synthesize RNA primers</p> Signup and view all the answers

    What is the term for the process of replication where the new DNA molecules contain one old strand and one new strand?

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

    Which of the following statements is TRUE regarding DNA replication?

    <p>The energy for DNA synthesis comes from the removal of the two phosphates of the incoming nucleotide.</p> Signup and view all the answers

    What does the term "semi-conservative replication" refer to in the context of DNA replication?

    <p>Each daughter DNA molecule contains one strand from the parent DNA molecule and one newly synthesized strand.</p> Signup and view all the answers

    What is the role of the "old" DNA strand in DNA replication?

    <p>The &quot;old&quot; DNA strand serves as a template for the synthesis of the new strand.</p> Signup and view all the answers

    Why is the direction of DNA synthesis always 5' to 3'?

    <p>The enzymes involved in DNA synthesis can only add nucleotides to the 3' end of a growing DNA strand.</p> Signup and view all the answers

    What is the significance of the fact that DNA is synthesized in a 5' to 3' direction?

    <p>It ensures that the genetic information is copied accurately from the template strand.</p> Signup and view all the answers

    What is the initial step in the DNA replication process?

    <p>Formation of the origin of replication</p> Signup and view all the answers

    Which enzyme is primarily responsible for synthesizing new DNA strands during replication?

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

    Which of the following correctly describes the elongation phase of DNA replication?

    <p>DNA polymerase synthesizes new strands.</p> Signup and view all the answers

    What occurs during the termination phase of DNA replication?

    <p>Replication forks meet and DNA synthesis is completed.</p> Signup and view all the answers

    Which statement about the origin of replication is accurate?

    <p>It is the starting point for replicating DNA strands.</p> Signup and view all the answers

    Study Notes

    DNA Overview

    • Deoxyribonucleic Acid (DNA) is a nucleic acid located in the nucleus.
    • DNA is a polymer composed of nucleotides, each containing:
      • A deoxyribose sugar (5-carbon sugar)
      • A phosphate group
      • A nitrogenous base

    Nitrogenous Bases

    • Four nitrogenous bases in DNA:
      • Purines: Adenine (A), Guanine (G)
      • Pyrimidines: Thymine (T), Cytosine (C)

    Structure of DNA

    • DNA is structured as a double helix, with two nucleotide strands.
    • Strands run in antiparallel directions, meaning they orient differently.
    • Hydrogen bonds form between bases: A pairs with T, C pairs with G.
    • The "ladder" structure consists of a sugar-phosphate backbone and base pairs as rungs.
    • During replication, the parent strand acts as a template for producing daughter DNA strands.

    DNA Replication Process

    • Replication is semi-conservative; each new DNA molecule contains one old strand and one new strand.
    • Replication occurs in the 5' to 3' direction.
    • Energy for synthesis derives from the removal of two phosphates from incoming nucleotides.
    • Replication features:
      • Initiation occurs at specific origins.
      • Bidirectional movement is typical during synthesis.
      • Strands elongate in a 5' to 3' direction and are semi-discontinuous.

    Requirements for DNA Replication

    • Requires several key components:
      • Templates from both strands of parental DNA.
      • Nucleotides: dATP, dTTP, dGTP, dCTP.
      • Enzymes: DNA polymerase, helicase, primase, ligase.
      • RNA primer for initiating synthesis.
      • Single-strand binding proteins (SSB) for stabilization.
    • Proofreading occurs as an error control measure during replication.

    Leading and Lagging Strands

    • The leading strand is synthesized continuously in the same direction as the replication fork.
    • The lagging strand is synthesized discontinuously, moving away from the replication fork, forming short segments known as Okazaki fragments.

    Steps of DNA Replication

    • DNA replication in prokaryotes begins at a single origin and travels bidirectionally around the circular DNA molecule.
    • Three primary steps in replication:
      • Initiation: The process begins at the origin of replication.
      • Elongation: DNA polymerase synthesizes new DNA strands.
      • Termination: The replication process concludes once the entire molecule is copied.

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    Description

    This quiz covers the basics of DNA, its structure, and replication process. It explores the composition of nucleotides, phosphate groups, and nitrogen-containing bases.

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