DNA Structure and Composition
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Questions and Answers

What is the approximate diameter of the DNA molecule according to the double helix model?

  • 4 nanometers
  • 2 nanometers (correct)
  • 1 nanometer
  • 5 nanometers

    • What are the two components of the sugar-phosphate backbone of the polynucleotide chain?

  • Phosphate groups and nitrogenous bases
  • Nitrogenous bases and phosphodiester bonds
  • Sugar molecules and nitrogenous bases
  • Sugar molecules and phosphate groups (correct)

    • What is the function of the phosphate groups in the sugar-phosphate backbone?

  • They facilitate the replication of DNA
  • They act as a binding site for nitrogenous bases
  • They give the backbone a negative charge (correct)
  • They provide structural support to the backbone

    • What is the composition of a nucleotide?

    <p>A sugar molecule, a phosphate group, and a nitrogenous base</p> Signup and view all the answers

    According to the base pairing rules, which base pairs with Thymine (T)?

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

    What is the function of the phosphodiester bonds in the polynucleotide chain?

    <p>They link nucleotides together</p> Signup and view all the answers

    What type of bond is formed between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of another?

    <p>Phosphodiester bond</p> Signup and view all the answers

    What is the approximate pitch of the double helix structure?

    <p>3.4 nanometers</p> Signup and view all the answers

    What is the characteristic shape of the double helix model of DNA?

    <p>A right-handed spiral staircase-like structure</p> Signup and view all the answers

    Study Notes

    Polynucleotide Chain Structure

    Double Helix Model

    • The double helix model describes the 3D structure of DNA
    • Two complementary polynucleotide chains twisted together
    • Chiral, with a right-handed spiral staircase-like structure
    • Diameter: approximately 2 nanometers (nm)
    • Pitch: approximately 3.4 nm (10 base pairs)

    Sugar-Phosphate Backbone

    • The backbone of the polynucleotide chain is composed of:
      • Sugar molecules (deoxyribose in DNA)
      • Phosphate groups
    • The sugar and phosphate molecules alternate in a repeating pattern
    • The backbone is negatively charged due to the phosphate groups

    Nucleotide Composition

    • A nucleotide is composed of:
      • A 5-carbon sugar (deoxyribose in DNA)
      • A phosphate group
      • A nitrogenous base (A, C, G, or T)
    • Nucleotides are linked together through phosphodiester bonds

    Base Pairing Rules

    • Adenine (A) pairs with Thymine (T) through two hydrogen bonds
    • Guanine (G) pairs with Cytosine (C) through three hydrogen bonds
    • Base pairing is complementary, with each base having a specific partner
    • Base pairing is responsible for the stability of the double helix structure

    Phosphodiester Bonds

    • Phosphodiester bonds link nucleotides together in a polynucleotide chain
    • Formed through a condensation reaction between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of another
    • Phosphodiester bonds are strong covalent bonds that hold the backbone together

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    Description

    Learn about the double helix model of DNA, the sugar-phosphate backbone, nucleotide composition, base pairing rules, and phosphodiester bonds. Understand the structure and composition of DNA molecules.

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