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Senanu's Bio class

Chapter 15 – DNA

OBJECTIVE: Describe the historical pathway and series of experiments that led to the discovery that DNA is the genetic material

  1. Why did Griffith’s mice die when injected with a mixture of dead pathogenic bacteria and live non-pathogenic bacteria? (this experiment is explained in the online videos)
  2. What was the basic conclusion from the Hershey-Chase experiment?

  3. Who, and in what year, figured out the secondary structure of DNA?

    OBJECTIVE: Describe the structure of the DNA double helix and the structure of chromosomes.

  4. What are Chargaff’s base-pairing rules?
  5. Which bases are purines?
  6. Which bases are pyrimidines?
  7. Why must a purine always bind to a pyrimidine?
  8. Which bases are ‘complementary’ to one another?
  9. What were the basic conclusions from the Meselson-Stahl experiment?
  10. Draw and label a diagram of a DNA monomer.
  11. Draw a diagram/model of the DNA double helix that illustrates complementarity, antiparallel strands.

  12. How are prokaryotic chromosomes different from eukaryotic chromosomes?

    OBJECTIVE: Understand when DNA replication occurs and the main enzyme involved in the process.

  13. Onto which end of the DNA strand are nucleotides added? (commit this to long-term memory – it will serve you well). Draw a diagram of this.
  14. On page 322, your book states that DNA synthesis is bidirectional. How does this square with the previous question?
  15. Why is synthesis of the leading strand different from synthesis of the lagging strand?
  16. Write brief descriptions of what each enzyme or protein below does in the replication of DNA:
    • Helicase
    • single-strand binding proteins
    • topoisomerase
    • primase
    • DNA polymerase III
    • DNA polymerase I
    • Ligase
  17. What role do DNA polymerase I and DNA ligase play? Why are they necessary on the lagging strand but not on the leading strand?
  18. What is the difference between proofreading and mismatch repair?
  19. Why is ligase required at the end of excision repair?
  20. What problem does telomerase solve?
  21. When in an organism’s life is telomerase active? When is it inactive?