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RT 230 - Radiation Biology Exam 2006
Answer Key
MULTIPLE CHOICE.
On the line to the left, place the letter of the choice that best
answers the question. Three Points Each. NOTE: "e" answers are never the correct
answer.
1. Radiation sensitivity is
___C___ a. Roughly equal between embryo and infant
b. Highest during adolescence
c. Lowest during adulthood
d. Lowest in adulthood and old age
e. Do we really care if radiation is easily upset-?
...it is related to cell division and active repair - highest in embryos,
lowest in adults (it goes up with aging
again because repair ability drops off).
2. Telomere activity is an important aspect in
___A___
a. Aging
b. Radiation absorption
c. Gene expression
d. Target theory
e. Processes that no one cares about
...it's the chromosome "cap" that "frays" during DNA replication unless
fixed by an enzyme - and we stop
making that enzyme in late adolescence / early adulthood.
3. In the term LD50/60, the 60 part represents
___C___ a. Percent of the group
b. Percent of cells
c. Days
d. Hours
e. How many times I'm beating myself up for forgetting this
...LD is Lethal Dose, the 50 is 50% dead, and the 60 is within 60 days.
4. In the oxygen enhancement ratio, what does the oxygen enhance?
___D___ a. Cell recovery
b. Gene expression
c. Image contrast
d. Radiation sensitivity
e. It lets the natural beauty shine through
...oxygen's presence magnifies chemical effects of the radiation.
5. A person can become radioactive if
___B___ a. They absorb enough radiation
b. They take in radioactive materials
c. They absorb the "right" kind of radiation
d. All of the above
e. Um, wait a minute...
...you can't really radiate unless you've taken in and are storing, however
briefly,
some sort of radiating material.
6. Radiation damage to proteins has limited impact on cells because
___C___ a. Proteins are very difficult to damage
b. They can only be hurt directly
c. Cells normally deal with damaged proteins anyway
d. Cells don't depend much on proteins
e. Even undamaged proteins are really annoying
...proteins normally wear out and need to be replaced - a damaged protein is
treated as worn-out.
7. A single point mutation that substitutes one nucleotide for another will
change how much of a codon?
___D___ a. All of it
b. One half
c. One fifth
d. One third
e. A smidge
...this is a tricky way of asking, "How many nucleotides in a codon?"
8. The problem with known radioprotectors is that they are
___B___ a. Much too expensive
b. Highly toxic
c. Not selective enough
d. Sensitive to water content
e. Not available in enough stylish colors
...it's also not clear how to not get them just into the cells you
want to damage.
9. Which comes closest to expressing the idea of hormesis?
___A___
a. A little radiation is good for a person
b. Any radiation at all is bad
c. Diagnostic exposure is worth the risk
d. You can appear healthy but still be dying
e. Weird words on exams are never a good sign
...it can be applied to things other than radiation. For radiation,
the evidence isn't there.
10. X ray exposure on the atomic level can cause the loss of
___C___ a. Protons
b. Neutrons
c. Electrons
d. All of the above
e. Bladder control
...that's what makes it ionizing radiation.
11. When a cancer metastasizes, the cells
___D___ a. Divide much faster
b. Become resistant to treatment
c. Begin to change the cells around them
d. Begin to migrate
e. Pick up a major ‘tude
...that's the great threat - they spread tumors.
12. Radiation-induced blindness is most likely to result from
___B___ a. Retinal detachment
b. Cataracts
c. Glaucoma
d. Macular degeneration
e. Looking at too many patients in those gowns
...it's the part of the eye most likely to be damaged.
Short Answer.
Pick SIX questions to answer in the spaces
provided.
NOTE: if you answer MORE than six, only the first six will be corrected.
Four Points each. Partial credit is possible.
| 1. What are two pathways by which
radiolysis of water can have indirect damaging effects in a cell? |
| Free radicals |
Hydrogen Peroxide |
2. In target theory, what is the target?
...A molecule that is critical to a cell's
survival.
|
| 3. What are four different types of
cellular organelles found in the cytoplasm? |
|
Mitochondria |
Endoplasmic reticulum |
| Golgi
Bodies |
Ribosomes |
|
Vacuoles / Vesicles |
Lysosomes |
4. In general, what's the relationship between the
linear energy transfer (LET) of a radiation type and its penetration
ability?
...the higher the LET (all other things being
more-or-less equal), the less the penetration - the beam loses energy
transferred to the surroundings and eventually loses its energy
entirely. |
| 5. What two aspects of the prodromal
period is used to guess how severe a radiation dose a person has
received? |
| Severity of
symptoms |
Lag time between
dose and symptom onset |
| 6. What two parts of a human cell both
have DNA in them? |
| Nucleus |
Mitochondrion |
7. What's an SED50? Don't just say what that stands
for - what is it?
...it's the dose at which 50% of a study
population gets skin erythema. |
8. What is apoptosis?
...it's a cell purposely dying, usually when it
has been "told" to. |
9. Pick one type of risk assessment - name it and
describe how it's assessed.
Relative Risk - cases compared
to number expected.
Excess Risk - cases beyond expected in a population.
Absolute Risk - cases expected in a
particular group.
|
| 10. Under the Law of Bergonie and
Thibodeau, what are two features found in cells that increases their
vulnerability to radiation? |
| Undifferentiated
Spend more time dividing |
Have greater
reproductive / division activity |
11. Why are most point mutations essentially neutral
in effect?
...they hit no-coding areas, or change the code
in a way that doesn't affect the coded protein. |
12. Pick one cellular component of blood. Name it,
and explain how radiation exposure to bone marrow affects their levels
in the blood over time.
White Blood Cells - Used fighting initial
tissue damage effects, not replaced, drop soon after stored cells are
exhausted.
Platelets - Used while tissue damage results in minor bleeding, then
drop slowly.
Red Blood Cells - Not much affected
- levels drop eventually, when cells wear out and are not replaced. |
| 13. What are two different factors that
can produce a threshold effect for radiation damage? |
Radiation type,
particularly the LET -
higher LET, more damage, lower theshold |
Dose, high enough
to provide multiple hits to many cells. |
Long Answer.
Select and answer completely any four of the
following questions.
Note: if you answer more than four, only the first four will be corrected.
Ten Points Each. Partial credit is possible.
| 1. For gonad exposure in the two genders,
briefly fill in the information. |
| |
Time Period over which most effects from
radiation damage will show up |
Why this particular time period |
|
MALE |
Within two months of exposure
|
Affected cells are either removed (sperm-making cells) or have left the
body (sperm). |
|
FEMALE |
Puberty to menopause
|
Affected egg cells will not show effects until after ovulation and
fertilization. |
| 2. For three general types of tissue,
name the type, give the general radiosensitivity (low / medium / high,
possibly ranges), and explain why it has that sensitivity. |
| TISSUE TYPE |
RADIOSENSITIVITY |
Explanation |
|
EPITHELIUM |
High |
Cells
typically dividing. |
|
CONNECTIVE |
Medium
- High |
Division rate varies, but division is common. |
| MUSCLE |
Low |
Cells
rarely divide. |
| NERVOUS |
Low |
Cells
rarely divide. |
|
REPRODUCTIVE |
High |
Cells
divide a lot when active. |
| 3. For the three acute radiation
syndromes, give the name of the syndrome, then briefly explain the
reason why it has its effects (types of tissue affected & result of
effects). |
|
Hematologic or Hematopoietic or Bone Marrow |
Blood-making cells are affected, so new cells are not made - as old ones
are used up or wear out, there are no replacements |
|
Gastrointestinal |
Lining
cells are affected, compromising digestion, water balance, and
protective mucus effects. |
| Central
Nervous System |
May be
from capillary leakage and pressure or direct chemistry effects on
workings of the brain and spinal cord. |
| 4. Briefly explain, step-by-step, the most common way
radiation can bring about the death of a tumor. Talk about what's going
on in the cells. |
| High-dose
beam absorbed by tumor cells.
Radiation breaks DNA
in cells multiple times.
DNA is repaired, but
not properly, leaving pieces free of their original chromosomes.
DNA is replicated as
preparation for cancer cell division.
As duplicate
chromosomes are organized and distributed in cell division, free pieces
are not controlled.
Many daughter cells
wind up with extra or missing chromosome pieces.
Cells try to use
genes on those pieces, affecting chemistry of cells, to the point that
they die.
All cells of tumor
either die or cease to divide, effectively killing tumor.
|
| 5. What are five different sorts of
cellular effects of radiation damage? |
Instant Death |
|
Reproductive Death / Can't reproduce |
Apoptosis -
purposely brings about own death |
| Mitotic
Death / dies during, shortly after division |
Mitotic delay |
|
Interference with function |
Breakage of
chromosome |
| 6. What are five different types of
cancer that have been directly linked to radiation damage? |
Leukemia |
| Thyroid |
Bone |
| Skin |
Breast |
| Lung |
Liver |
| 7. There are four basic factors that
determine, in general, the amount of damage that radiation will do. What
are they? |
| Type of radiation |
Dose of radiation |
| Tissues irradiated |
Timing of dose |
BONUS QUESTIONS.
Answer as many as you are able. Wrong answers
will not result in points being lost from the main exam. You can get partial
credit on these answers.
How does the radiation in a microwave oven cause food to heat up? Three Points.
Why, probably, does a heavy dose of radiation cause a mobilization of white
blood cells? Three Points.
A diagnostic x-ray represents a unit of 1 on what scale? Three Points.
The "rules" of cell-survival kinetics are worked out in cell cultures. Why might
that be unreliable? Three Points.
Briefly explain the idea behind Poisson distribution. Three Points.
What is forecast to happen to 25% of the people on any mission to Mars? Three
Points.
In general, what common factor has the biggest effect on shortening life span?
Three Points.
Briefly explain the effect that cross-linking may have on stereospecificity.
Three Points.
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