Physics 108 Lecture 38: Biological Effects of Radiation

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Physics 108 Lecture 38 Biological Effects of
Radiation
Important Cell Biology

• All cells have _______ pairs of ________________,
  for a total of __________.
• Chromosomes consist of strands of __________ that
  have protein synthesizing instructions .
• ___________ are
• sets of instructions for individual proteins.
• _______________ when passed down as 23
  chromosomes from each parent combine to make a 46
  chromosome zygote.
• ________________ when chemically changed.

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Types of Biological Effects of Radiation

• _________________ - the higher the radiation
  dose, the higher the probability that the effect
  will occur.
• Examples
• _________________ - the higher the radiation
  dose, the more severe a guaranteed effect will
  be.
• Examples
• _________________ - molecular bonds are broken
  during ionization events.
• _________________ - ions formed during ionization
  recombine into new and possibly different
  chemicals than their original form.

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What happens to Irradiated Cells?

• ___________________
• Reproductive death occurs because cell ceases to
  undergo mitosis.
• Occurs more easily with regularly reproducing
  cells such as the intestine than with longer
  lived cells such as muscle or bone.
• Has a dependence on the amount and type of
  radiation (see diagram)
• __________________
• Is manifested as rapid, uncontrolled cell
  division.
• Is caused by radiation acting like a carcinogen,
  in that it causes certain specific chemical
  changes in the cells.
• Is a latent effect only observed generations of
  cells later than the initial radiation dose is
  received.
• ____________________
• Occur when genes are chemically changed due to
  the indirect effects of radiation.
• Have physical significance because different
  proteins are produced in the cell than originally
  instructed by the DNA sequencing.
• Mostly are never observed because either the
  cells themselves or later generations of cells
  die due to producing the wrong proteins.
• Are of most concern with cells in the gonads due
  to the potential to pass on mutated protein
  instructions to ALL cells in the offspring of a
  parent.

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Survival Curve for Cell Killing after acute
radiation
Survival fraction ()
Dose (rad)
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When are biological effects of radiation observed?

• ____________________doses of 10-20 rem
  (__________ Sv) or more
• ____________________doses of less than 10 rem
  (_____ Sv) several times
• ____________________doses of millirems (
  ____________ Sv) received daily

Large acute doses early biological effects

• Generally non-stochastic, less than 2 months time
  before effect is observed
• ____________________
• ____________________
• ____________________
• ____________________
• ____________________
• ____________________

Note the higher your dose, the more severe the
problems are. The most severe effects are only
observed with doses over 200rem
Large acute doses late biological effects

• Generally stochastic, usually more than 2 months
  before effect is observed
• ____________________ ____________________
• ____________________ ____________________
• ____________________ ____________________

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Chronic low doses

• Data is generally inconclusive because
  probabilities of observing effects such as cancer
  do not always show increased risk when receiving
  chronic low doses of radiation. See notes on
  dose response curve below.

possible shape cell killing begins to occur
well documented
Increased probability of seeing Effect (cancer)
data does not confirm accepted linear
extrapolation model
data confirms maybe will be accepted
dome data confirms probably will not be accepted
hormesis radiation is good for you
Dose (rem)