1. Criteria for DNA to be accepted as genetic material
    Present in nuc and chromosomes, doubles in cell cycle, twice abundance in diploid, same pattern of transmission as its genetic information
  2. DNA was found by
  3. What did Miescher do with cells
    Isolated nuclei, fibrous substance nuclein was extracted. DNA was found in chromosomes using dyes.
  4. To help support Miescher’s theory, what did they do with stained cells
    They put them through a flow cytometer
  5. What did putting cells through flow cytometer do for miescher
    Helped prove that nondividing cells have some amount of nuclear DNA and after meiosis, gametes have half
  6. What happens when a virus affects a bacterium
    It injects only its DNA to change the genetic program of the bacterium.
  7. A type of experiment that showed that DNA from one strain could genetically transform to another
    Transformation experiment.
  8. Two questions that scientists wanted to answer about DNA
    How is it replicated and how does it direct protein synthesis.
  9. Who discovered shape of DNA
    Rosalind Franklin. She saw it was spiral through crystallographs.
  10. Who found that A=T and C=G
    Erwin Chargraff; chargraff’s rule.
  11. Who built a model of dna and saw it was antiparallel and helical
    Crick and Watson
  12. What did Watson and crick suggest about shape of DNA
    Phosphate backbone, nucleotides on inside, base pairs have same width down helix
  13. 4 key features of DNA structure:
    Double-stranded helix, right handed, antiparallel, outer edges of bases are exposed in major and minor grooves
  14. Why do dna grooves exist
    Because the backbone of dna strands not evenly spaced
  15. What are the outer edges of the base pairs on DNA exposed to?
    Hydrogen bondng.
  16. Surfaces of AT and GC base pairs are
    Chemically distinct
  17. 4 important functions of DNA
    Storage of info, replication, susceptibility to mutation, expression of coded info as phenotype
  18. What does semiconservative replication mean
    That each parental strand serves as a template for a new strand.
  19. What are 2 steps of DNA replication
    Unwind double helix so two templates are available, and two nucleotides form the base pairs with template strands that are linked together by phosphodiester bonds
  20. The template DNA is read in this direction
  21. During DNA synthesis, where are nucleotides added and why
    To 3’ end of strand because of free hydroxyl group (OH-)
  22. dNTP’s stands for
    deoxyribonucleoside triphosphates aka deoxyrybonucleotides
  23. these are the building blocks of DNA, where two phosphate groups are released and 3rd is bound to 3’ end
  24. what does DNA replication begin with?
    The binding of a large protein complex to a specific site on the DNA molecule
  25. What does the large protein complex contain? What does it do?
    It contains DNA polymerase which catalyzes addition of nucleotides.
  26. Where does the large protein complex bind to
    The ori… origin of replication
  27. Where does the DNA unwind
    Replication fork
  28. How would replication be sped up
    If a chromosome was linear and had multiple origins of replication
  29. What do you first need to begin DNA replication
    A primer- a starter strand; it is complementary to the dna Template. You then need a primase (enzyme) to synthesize dna one nucleotide at a time.
  30. Where does DNA polymerase add nucleotides
    To the 3’ end
  31. DNA polymerases are larger than
    Their substrates, dNTPs, and the template DNA
  32. In the hand shape enzyme, what does the palm and fingers do
    Palm bring the active site and substrate together, fingers recognize nucleotide bases
  33. What direction does DNA replicate
  34. How is the leading strand oriented to grow
    It grows it’s 3’ end as the fork opens
  35. How is the lagging strand oriented
    So that its 3’ end is exposed and gets farther from the fork.
  36. What are okazaki fragments
    Synthesized lagging strands that occur in small discontinuous stretches
  37. What does each okazaki fragment require?
    It requires its own primer, synthesized by primase
  38. How does fragmentation happen in Okazaki fragments
    DNA polymerase adds nucleotides to 3’ until it reaches the primer of the previous fragment, a different DNA polymer replaces primer with DNA. The final phosphodiester linkage is catalyzed by DNA LIGASE
  39. DNA polymerase is very fast and it is processive. What does this mean?
    It means it catalyzes many sequential polymerization reactions each time it binds to DNA.
  40. Okazaki fragment are added to RNA primers for what purpose
    To replicate lagging strand
  41. When does fragmentation end in okazaki fragments
    When the last primer is removed because there is no more 3’ to extend.
  42. What happens to the ends of okazaki fragments
    The ends are cut after replication and chromosome is slightly shortened after each division
  43. What are telomeres
    Repetitive sequences at the ends of eukaryotic chromosomes.
  44. What do telomeres do
    They prevent the chromosome ends from being joined by DNA repair system
  45. What is telomerase and what does it do
    It contains RNA sequence; acts as template for telomeric DNA sequences. Lost over time in most cells but not in cells that continuously divide, like bone marrow and gametes

    • How can errors in DNA replication be fixed
    • Proofreading, mismatch repair
  46. How does proofreading work in repair mechanisms
    If bases are paired incorrectly, the nucleotide is removed
  47. How does mismatch repair work in repair mechanisms
    Other proteins scan for mismatched bases missed during the proofreading. They them replace them with the correct ones
  48. That are the 5 things that PCR technique requires
    Double stranded DNA sample, two short primers complementary to ends of sequences to be amplified. Four dNTPs, a DNA polymerase that works at high temps, Salts and buffer
  49. Changes in the nucleotide sequence of DNA that are passed on from one cell to another
  50. Two ways errors that are not corrected can be passed on to daughter cells
    Somatic mutations & germ line mutations
  51. What are somatic mutations
    They occur in somatic cells; passed on by mitosis bu not to sexually produced offspring
  52. What are germ line mutations
    Give rise to gametes; passes mutation at fertilization.
  53. Which type of mutations do not affect protein function
    Silent mutations
  54. What happens in a loss of function mutation?
    Proteins are affected and may lead to structural proteins or enzymes that don’t work anymore; they are almost always recessive
  55. What happens in a gain of function mutation
    It leads to a protein with an altered function
  56. What is a conditional mutation
    It means the phenotype will work under restrictive conditions, maybe temperature, but may not be detectable under permissive conditions
  57. What are the two categories of mutations
    Point and chromosomal
  58. What is a point mutation
    It results from the gain, loss or substitution of a single nucleotide
  59. What is a chromosomal mutation
    It is more extensive than a point mutation; it may change the position of cause a DNA segment to double or disappear
  60. What are two types of chromosomal mutations
    Deletions, inversions, translocations, duplications
  61. What is a deletion mutation?
    The part of genetic material is removed; can be fatal
  62. What is a duplication mutation?
    Homologous chromosomes break and recombine incorrectly; it may have two copies of segment while the other has none
  63. What is an inversion mutation
    It results from breaking and rejoining.. only the segment is ‘flipped’
  64. What is a translocation mutation
    Segment of DNA breaks off and is inserted to another chromosome; can lead to duplications and deletions
  65. How are mutations caused
    Spontaneously and inducedly
  66. What are some types of spontaneous mutations?
    Errors in replication by polymerase; bases have different structures (tautomers); chemical rxns change bases; imperfect meiosis; gene sequences disrupted
  67. What are some types of induced mutations?
    Chemicals alter nucleotide bases; chemicals can add bases
  68. What types of radiation damage DNA
    Ionizing radiation and UV radiation
  69. What happens in ionizing radiation
    Free-radicals are ccreated and are highly reactive. Can change bases and break sugar phosphate bonds
  70. What happens in UV radiation.
    The radiation is absorbed by thymine and it forms covalent bonds with nearby nucleotides, disrupting DNA replication
  71. Where do mutations occur most often
    At base pairs
  72. What are some benefits of mutations
    Raw material for evolution (genetic diversity); the diversity may benefit the organism somatically; may have advantageous changes in future offspring
  73. What can we learn from ancient DNA?
    If some is left, we can PCR it. We learn that Neanderthals have 99%% identical DNA to humans. Had fair skin & red hair, were probably capable of speech and interbred with humans
Card Set
ch 9