Chapter 12

  1. What is the evidence that the gene is DNA?
    DNA from one type of bacterium genetically transforms another type.

    The transforming principle is DNA.

    Viral replication experiments confirmed that DNA is the genetic material.

    Eukaryotic cells can also be genetically transformed by DNA.
  2. What is the chemical composition of DNA?
    Sugar deoxyribose

    A phosphate group

    • A nitrogenous base
    • - purines: adenine and guanine
    • - pyrimidines: cytosine and thymine
    • A&T, G&C
  3. What is the structure of DNA?
    • The double-helix formation of uniform diameter.
    • It is right handed.
    • It is anti-parallel.
    • Bases are located on the interior of the structure while the sugar-phosphate backbone are on the exterior of the structure.
  4. What are the three modes of DNA replication?
    Semiconservative replication- produces molecules with both old and new DNA.

    Conservative replication- would preserve the original molecule and generates an entirely new molecule.

    Dispersive replication- would produce two molecules with old and new DNA interspersed along each strand.
  5. What are the two steps in DNA replication?
    The DNA double helix is unwound to separate the two template strands to make them available for new base pairing.

    As new nucleotides form complementary base pairs with template DNA, they are covalently linked together by phosphodiaster bonds, forming a polymer whose base sequence is complementary to the bases in the template strand.
  6. What is proofreading?
    A mechanism that corrects errors in replication as DNA polymerase makes them.
  7. What is a mismatch pair?
    A mechanism that scans DNA immediately after it has been replicated and corrects any base-pairing mismatches.
  8. What is excision repair?
    A mechanism that removes abnormal bases that have formed because of chemical damage and replaces them with functional bases.
  9. How are errors in DNA repaired?
    By proofreading, mismatch repair, and excision repair.
  10. What are telomeres?
    Repetitive sequences that are at the ends of chromosomes, in many eukaryotes.

    In humans TTAGGG
  11. Telomerase
    An enzyme that catalyzes the addition of any lost telomeric sequences in the cells. It keeps the cells staying active for more and more multiple cell division. (rapid growth)

    ex. Cancer or bone marrow stem cells.
Card Set
Chapter 12
DNA and its role in heredity