RT 230 - 2007 Exam McDarby

RT 230 - Radiation Biology Exam 2007
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. Which is an example of hormesis?

___B___   a. Once a cell takes a critical hit, additional exposure doesn't matter
                b. A glass of wine a day may help prevent cancer
                c. DNA is needed to make proteins, but proteins help make DNA
                d. A single diagnostic x-ray might cause leukemia
                e. Isn't that some sort of luncheon meat?

...this is the idea that small amounts of something that is harmful in large amounts can actually be beneficial.
- In this case, alcoholic beverages. This is sometimes applied to radiation.

2. What happens at the dose-response threshold?

___C___ a. Effects become linear b. Effects stop being linear c. Effects appear
d. Effects produce cell death e. Something grabs onto a thres and won't let go

...below the threshold, no effects.

3. Telomeres are most likely to degrade during

___D___ a. Protein production b. Chemical damage c. Radiation damage
d. Chromosome duplication e. De marking period

...they are the "endcaps" that need to be fixed after duplication, but sometimes aren't.

4. A cell is most likely to be severely affected by radiation if the exposure is

___D___ a. Mutated b. Ionized c. Between divisions d. During a division e. Particularly embarrassing

...normal repair chemistry isn't working during a division, and since the chromosomes are all wrapped up for movement,
repair enzymes codes can't be accessed to make them.

5. Cross-linking happens between

___B___ a. Data and risk groups b. Molecules c. Chromosomes and mutations
d. Therapeutic beams e. The stuff I know and the stuff I'm confused about

...it can be something that radiation-induced breakage or destabilization produces - molecules connect to molecules they
shouldn't.

6. Very energetic radiation may have a low LET because –

___C___    a. It affects primarily DNA                                                    b. It does not penetrate very far
                c. It does not interact much with material in the cells                d. It gets absorbed by water
                                                                e. It lost it playing the lottery

                    ...which is the definition of Linear Energy Transfer.

7. Relative risk is relative to what?

___B___    a. The exposed group's number                 b. The expected number                c. The maximum number
                d. Zero                                e. How much risk can a risk group have if a risk group must risk risk?

...it's used to detect effects in groups, when something shows up more (or less) than it should.

8. Of the various gene point mutations,

___C___ a) Substitutions are worse than deletions                b) Insertions are worse than deletions
                c) Substitutions often have no effects                  d) Insertions often have no effects
                                                e) I don't remember the point

...a point substitution often produces a new codon, but it codes for the same or a related amino acid in
the protein, so the protein isn't any different.

9. Which is not a statement from the Cell Theory?

___A___    a. Cells always have membranes                                        b. Cells are more similar than different
                c. All living things are made up of at least one cell                d. Cells are the smallest things that are considered alive
                                                e. Cells may be the most boring things in existence

...it is a true statement, but it's not from the Cell Theory.

10. According to the mathematics of target theory, if a group of cells is hit with just enough radiation to theoretically hit every cell with a lethal dose,
how many will probably die?

___B___ a. 100% b. 63% c. 37% d. 0% e. Math...gack...sputter...ack...

...about 2/3 get hit (many more than once) and 1/3 get missed.

11. An SED50 is a term applied to

___D___ a. Serious effects b. Sperm effects c. Stomach effects d. Skin effects e. Sudoku education

...stands for Skin Erythema Dose - 50% of exposed group.

12. The higher the oxygenation level of an area,

___A___    a) The greater the radiation effect                                    b) The lower the radiation effect
                c) The fewer free radicals                                                d) The more likely it is to be cancerous
                                                e) The bubblier it is, like champagne in your guts

...it's an Oxygen Enhancement Ratio...

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. For radiation fractionation -
Definition- Delivering an overall dose in separate exposures.	Why effect may be less- Exposed cells get a chance to recover between exposures.

2. Give two aspects of gastrointestinal syndrome that can actually bring about someone's death.
Lack of nutrition - lining loss prevents absorption of nutrients. Dehydration - same problem with water.	Infection - loss of mucus protection can ulcerate lining and allow bacteria into blood. Blood loss - through same sort of ulceration.

3. Of the five basic tissue types, which two are least sensitive to radiation damage? These will be the ones with the lowest division potentials.
Muscle	Nervous tissue

4. What are two different types of problems that can be detected by inspecting a karyotype?

Extra or missing chromosomes

Chromosome breakage / missing or extra pieces

5. What are two factors that determine how much tissue damage radiation will do?

The amount of radiation.

The type of radiation.

The area (volume) of tissue exposed.

The types of tissues exposed.

6. What two aspects of the prodromal period is used to guess how severe a radiation dose a person has received?
The time between exposure and symptoms.	The severity of the symptoms.

7. Give two organelles found between the nucleus and the cell membrane, and for each give a function.
Mitochondrion - aerobic respiration.	Golgi Bodies - Packaging of secretions
Ribosomes - Protein production from gene codes	Endoplasmic reticulum - distribution channels
Vacuoles & Vesicles - Storage and specialty processing

9. What are two classes of gene types that can mutate and produce cancer? Think about the processes that, if gone wrong, can produce cancer cells.
Cell division.	Apoptosis (cell can't kill itself). Response to outside signals (which tell it to kill itself).

10. Explain what all the parts of the term LD50/60 mean.

The LD is Lethal Dose, the 50 is 50% of the group that dies (lethal), the 60 is within 60 days of exposure.

11. Briefly explain what happens in an atom during reradiation.

Radiation of one sort gets absorbed by an outer electron, causing it to jump to a higher orbit. It's very unstable out there, and "spits" out radiation in a different form to drop back down to where it was.

12. What are two features needed in a radioprotector?

Needs to do its job - protect cells from radiation damage.

Needs not to poison the owner of the 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 each reproductive system, explain how radiation damage patterns differ and why those patterns differ. Basic effects on the organs are more-or-less the same - it's the production of sex cells that really connects to the differences.

MALE:

Damage effects tend to only last maybe a month - sperm-producing cells that are damaged are gone by then because they've either died or become sperm, and even stored sperm are out of the system within a month.

FEMALE:

Damage effects can show up through the whole rest of the reproductive lifetime. Damaged egg cell production cells may not be used for years.

2. What are five possible cellular effects from radiation damage?	Instant Death.
Death during / just after division.	Not able to do mitosis.
Apoptosis.	Delay of mitosis.
Interference with normal function.	Breakage of chromosomes.

3. For hematologic / hemapoetic / bone marrow syndrome, the blood's cellular components disappear in a particular order. Put the components in that order, and explain why each takes longer / shorter times than the others

White Blood Cells - depleted early responding to widespread cell damage and infections.

Platelets - deal with blood vessel breakage, wear out.

Red blood cells - have decent amount stored in spleen, don't wear out very fast.

4. For five types of radiation-induced cancers that have been connected to a particular specific past exposure, give the cancer and the exposure type .
Leukemia	X-rays, even at diagnostic level.
Thyroid	Old treatments for thyroid disease, even newer treatments.
Bone cancer	Radium exposure.
Breast	TB treatment, Mastitis treatment, Atomic bomb survivors.
Lung	Inhaled radioactive particles, including radon.
Liver	Old imaging agent (thorium).

5. For the following life-time periods, rate the radiosensitivity (low, moderate, high) and give a brief explanation for why it has that sensitivity.
STAGE	RADIOSENSITIVITY	Explanation
Embryo	HIGH	Many undifferentiated, dividing cells.
Child	HIGH to MODERATE	Many cells divided, mostly differentiated.
Adult	LOW	Few cells divided, almost no undifferentiated cells.
Elderly	MODERATE	Cell repair chemistry not working well.

6. What are five different features that a malignant tumor probably has that would not be found in the other body tissues?	Cells are dividing very rapidly.
New blood vessels are being recruited into tissue.	Cells are almost totally undifferentiated.
Cells have no basic body function - take but give nothing back.	Cells are able to crawl through tissues and produce tumors elsewhere.
Cells are highly mutated, even with many chromosome abnormalities.	Cells are particularly sensitive to radiation damage.
Even very damaged cells tend not to kill themselves.

7. What are the cell characteristics for which the Law of Bergonie & Tribondeau apply? These increase their sensitivity to radiation damage.

Undifferentiated.

Dividing rapidly.

Spend most of their time dividing.

NO KEY FOR 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.

Cell membranes are a close-to-waterproof barrier. Why does an internal body cell need such a barrier around it? Three Points.

If radiation damaged the stereospecificity of a receptor, what exactly might change? Three Points.

Why exactly are radicals so reactive? Three Points.

In radiation damage, what's a deterministic relationship? Three Points.

Why did the firefighters who responded to the Chernobyl reactor meltdown risk their lives to fight the fire? Three Points.

Give one reason why there is no way to really tell what effects the levels of radon in residences might have. Three Points.

Why is there reason to think that the radon will have no real effect? Three Points.

What is likely to happen to a quarter of any Mars mission astronauts? Three Points.

Michael McDarby

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