Unit 2 (Molecular & Cellular Biology)

  1. **the interaction of radiation in cells is a probability function or a matter of:
  2. the initial deposition of energy occurs very rapidly – within a period of:
    10-17 seconds
  3. is radiation interaction in a cell selective or nonselective?
  4. as a generalization, visible changes in
    the cell's tissues and organs resulting from ionizing radiation are not:
    • not unique
    • they cannot be distinguished from damage produced by other types of trauma
  5. biologic changes resulting from radiation occur only after a period of time known as a ___________ which depends on ___________ and varies from _____________________.
    • latent period
    • dose and type of response
    • minutes to weeks to years
  6. results of ionizing radiation interacting directly with macromolecules (DNA, RNA, proteins, etc.):
    direct effect
  7. **absorption of ionizing radiation by the medium in which organelles are suspended, primarily water:
    indirect effect
  8. label A and B:
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    • A. direct effect
    • B. indirect effect
  9. **—atom or atom group carrying an unpaired electron and no charge:
    free radical
  10. **a free radical is highly reactive because the unpaired electron will pair up with another electron even if it has to:
    break a chemical bond
  11. **explain what is happening in the diagram:
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    • radiolysis of water
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    • radiation comes in, interacts with water (H2O), an electron is ejected (ionization), and the water molecule becomes positive
  12. **after radiolysis of water explain what can occur:
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    • free radical (-e) occurring after radiolysis attaches to a 2nd water molecule and gives it a negative charge (making it an anion).
  13. **after radiolysis, give a common reaction at this stage and explain it:
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    • following radiolysis, a positive water molecule can become a positively charged hydrogen ion and hydroxyl free radical
  14. **after radiolysis, give a common reaction at this stage and explain it:
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    • following radiolysis, a negative water molecule can become a negatively charged hydroxyl ion and a hydrogen free radical
  15. **describe what can occur with the following ion pair H+ and OH-
    • the ion pair may combine to form a water molecule (HOH). no damage would occur.
    • the ions may chemically react with cellular macromolecules
  16. **an example of an action of free radicals includes that they could come together. show what this would create with the free radicals H* and OH*
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    • no damage/harm occurs
  17. **an example of an action of free radicals includes that they could join with other free radicals, possibly forming a new molecule. show what this combination results in:
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    • hydrogen peroxide occurs, which is a bad reaction because this chemical breaks down cells; acts as a toxin/poison
  18. list three common actions of free radicals:
    • combine with each other
    • join with other free radicals, possibly forming a new molecule
    • react with normal molecules or biologic macromolecules, forming new or damaged structures
  19. **A free radical can combine with oxygen and form a:
    (give an example)
    • new free radical
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  20. **show a chemical reaction we discussed that is an example of when a free radical may react with a biologic molecule:
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    • R=any organic molecule
    • H=hydrogen
    • (RH) removing the H forms a biologic free radical
  21. —an indirect interaction usually produces __________ due to the presence of _________.
    • free radicals
    • oxygen
  22. **—if oxygen is present, R* and H* may react with oxygen to form:
    • RO2*
    • HO2*
    • can react with other organic molecules to cause biologic damage
  23. list the steps of the process of an indirect effect leading to biologic effects:
    • xray photon
    • fast electron
    • ion radical
    • free radical
    • chemical changes
    • biologic effects
  24. the rate at which ionizing radiation deposits energy as it travels through matter:
    LET (linear energy transfer)
  25. **what is LET measured in?
    • keV/µm
    • (keV of micrometers)
  26. **which has more LET, gamma or alpha and beta?
    alpha and beta are lower energy, therefore more attenuation, therefore have a higher LET as compared to gamma radiation
  27. produce ionizations that are distant from each other:
    • —low LET radiations
    • (ex. x and g rays)
  28. produce many ionizations in a short distance:
    • high LET radiations
    • (ex. a and neutrons)
  29. LET of x-ray, photoelectrons, and compton electrons:
    0.3 to 10 keV/µm
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    250 keV/µm
  31. **—dose from 250 kVp x-ray divided by the dose from another radiation source to produce the same biologic response:
    relative biologic effect (RBE)
  32. if the LET increases, what happens to the RBE?
  33. —a point mutation that commonly occurs with low-let radiations (high energy ionizing radiations):
    • single-strand break
    • repair enzymes can fix
  34. creates a frame shift mutation that can make a change in DNA:
    • double-strand break
    • not as easily repaired as a single-strand break
  35. with what type of radiation is a double-strand break more common?
    high LET, low energy ionizing radiation
  36. if a double-strand break is further exposed to radiation, what can result?
    additional breaks of the sugar-phosphate molecular chain 
  37. what can occur if a double-strand break occurs in the same rung of DNA?
    • results in cleaved or broken chromosome
    • if it divides, the daughter cell will receive incorrect genetic material
    • result can be death or impaired function of the daughter cell
  38. **usually the interaction of high energy/low LET with DNA causes a loss or change in nitrogenous base on the DNA called a:
  39. the chemical unions created between atoms by the single sharing of one or more pairs of electrons:
    • covalent cross-link
    • (at low energies, this process is caused from indirect action)
  40. radiation induced chromosomal breaks manifest during which phase(s) of cell division?
    • metaphase
    • anaphase
  41. what types of cells are subject to chromosome breakage?
    both somatic and reproductive cells
  42. chromosomal _____________ are when two or more segments appear.
  43. what are some occurrences that can happen when chromosomal fragments appear?
    • —they can rejoin to the original state
    • they can fail to rejoin and create an aberration (lesion or anomaly)
    • they can rejoin other broken ends and create new chromosomes that may not look structurally altered when compared to the original
  44. what are the two types of chromosome anomalies?
    • chromosome aberrations
    • chromatid aberrations
  45. when do chromosome aberrations take place?
    in early interphase (G1), before DNA synthesis has taken place
  46. when do chromatid aberrations take place?
    in late interphase (G2), after DNA synthesis has taken place
  47. label the types of damage that can occur in DNA:
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    • A. one side rail severed
    • B. both side rails severed
    • C. cross-linking
    • D. rung breakage
  48. after a low radiation dose, most cellular radiation damage that results in late somatic effects occurs because of:
    point lesions
  49. areas on DNA molecules caused by the breaking of a single chemical bond:
    point lesions
  50. **experimental data strongly supports that _____ is the irreplaceable master, or key, molecule that serves as the vital target.
    • DNA
    • (kills the cell)
  51. **KNOW the 7 key cellular effects of irradiation:
    • instant death
    • reproductive death
    • apoptosis/interphase death
    • mitotic/genetic death
    • mitotic delay
    • interference of function
    • chromosome breakage
  52. what exposure amount can cause cell death?
    • a gamma dose of 1000Gy can cause cell death in seconds or a few minutes
    • not caused in diagnostic exposure
    • ex. nuclear bomb
  53. in cell death, if enough cells of the same kind are killed, what can happen?
    a particular tissue or organ can be destroyed or seriously impaired
  54. what exposure amount can cause reproductive death?
  55. what is a positive aspect of reproductive death?
    it can prevent damage to further generations
  56. —**when a cell dies without attempting division during the interphase portion:
    apoptosis (programmed cell death)
  57. occurs when a cell dies after one or more divisions:
    mitotic death
  58. does mitotic death or apoptosis usually require more radiation dose to occur?
    • apoptosis
    • (small doses can cause mitotic death)
  59. failure of the cell to start dividing:
    mitotic delay
  60. what exposure amount can cause mitotic delay?
    1 rad
  61. reasons for mitotic delay:
    • —irradiation causing alteration of  a chemical involved with mitosis
    • proteins required for cell division not being synthesized
    • change in the rate of DNA synthesis after irradiation
  62. what occurs with the interference of function as an effect of irradiation?
    • —permanent or temporary interference of cell function
    • no affect on cell’s ability to divide
    • repair enzymes can fix damage and allow cell to function as normal with the exception of a small delay
  63. the potential result when ionizing radiation interacts with  a DNA macromolecule:
    • chromosomal breakage
    • (this can result in lost of genetic material and cause genetic mutations in future generations)
  64. **when broken ends of the chromosome rejoin with no visible damage:
  65. denoting a chromosome fragment without a centromere:
  66. chromosome having two centromeres:
  67. transportation of two segments of nonhomologous chromosomes:
  68. nonhomologous means:
    not identical
  69. when a broken chromosome segment is turned upside down:
  70. when the broken fragments relocate to opposite arms of the chromosome:
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    what is happening on the chromosomal level for this to occur?
    —acentric marker chromosome originating from 3q
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    what is happening on the chromosomal level for this to occur?
    a child with bisatellited, dicentric chromosome 15 arising from a maternal paracentric inversion of chromosome 15q
  73. how does downs syndrome occur?
    occurs when there are three strands in the 21st chromosome "pair"
  74. a condition classified by a flattened nose and face, upward slanting eyes, single palmar crease, short fifth finger that curves inward, widely separated first and second toes and increased skin creases:
    trisomy 21
  75. **a chromosome map produced when enlarged photographs of a cell’s chromosomes are cut out and each is paired with its sister chromosome:
  76. karyotypes of human somatic cells show:
    • 22 autosome pairs
    • 1 pair of sex chromosomes
  77. **records the relationship between an irradiated cell and the absorbed dose to determine radiosensitivity and is constructed from data obtained by a series of experiments:
    cell survival curve
  78. **what type of LET curve offers a survival shoulder?
    a low LET
  79. cell survival curve increases with:
    decreased dose and low LET
  80. list what these stand for:
    • LET: linear energy transfer
    • RBE: radiation biologic effect
    • OER: oxygen enhancement ratio
  81. if you have an increased RBE, what has happened to the LET? to the OER?
    both have increased (direct relationships)
  82. states that the radiosensitivity of cells is directly proportional to their reproductive activity and inversely  proportional to their differentiation:
    law of bergonie and tribondeau
  83. who observed the effects of ionizing radiation on testicular germ cells in rabbits and when?
    • j. bergonie and l. tribondeau
    • 1906
  84. the higher the metabolic rate of the cell, the _______ the sensitivity to radiation.
  85. hemopoetic cells are _____ sensitive to radiation than CNS cells.
    • more
    • (hemopoetic not as mature,constantly reproducing)
  86. cells respond differently to ionizing radiation depending on:
    • —metabolic rate
    • maturity
    • differentiation
  87. **describe how metabolic rate, maturity, and differentiation affect radiographic sensitivity:
    • higher metabolic rate: sensitivity increases
    • more maturity: sensitivity decreases
    • more differentiation: sensitivity decreases
  88. **know sensitivity doses for the following:
    hematologic depression
    whole body dose
    • hematologic depression: 25 rads
    • whole body dose: 500 rads
    • neutrophils: 50 rads
    • thrombocytes: 100-1000 rads
    • CNS: 5000 rads
    • spermatogonia: 200 rads temp, 500-600 rads permanent
    • ova: 500 rads, single exposure permanent damage
  89. undifferentiated (less specialized) and have rapid cell division:
    immature cells
  90. differentiated (more specialized) and have slow cell division:
    mature cells
  91. mature cells have ________ sensitivity than immature cells.
  92. small cell lung spreads quickly and is _____________ as opposed to non-small cell.
  93. **the only safe dose of radiation is:
    no dose at all
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    • single break, one arm, one chromosome
    • can have restitution, no damage
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    • single break, one arm, two chromosomes
    • can form acentric fragments & dicentric chromosome
    • translocation can occur
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    • double break, one arm, one chromosome
    • deletion or inversion can occur
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    • single break, both arms, one chromosome
    • inversion can occur
    • can result in acentric fragments and ring formation
    • possible functional alterations or cell death
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    dicentric fragment
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    acentric fragment
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    • translocation
    • —genetic material is rearranged but chromosome looks fine; inheritable characteristics are changed
    • —a mutation is produced
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    • inversion
    • —change in gene sequence with possible functional alterations or cell death
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    • restitution
    • no damage
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    • deletion
    • —loss of part of a chromosome or chromatid (genetic information)
    • aberration is produced
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    • ring formation
    • loss of genetic information
Card Set
Unit 2 (Molecular & Cellular Biology)
Unit 2: Molecular and Cellular Biology