HPS 420 FINAL EXAM

T/F: Direct ionization occurs only with electromagnetic radiation like X-rays and gamma rays.

False

T/F: Indirect action is the dominant mechanism of biological damage by low LET radiation like X-rays.

True

T/F: Neutrons cause ionization by directly interacting with electrons in atoms.

False

T/F: In the photoelectric effect, an inner-shell electron is ejected from the atom.

True

T/F: Pair production occurs only when photon energy exceeds >1.022 MeV.

True

T/F: Excitation results in ionization and the formation of ion pairs.

False

T/F: The wave model of electromagnetic radiation involves electric and magnetic fields oscillating perpendicularly. (wave model)

True

T/F: In direct action, radiation interacts directly with the DNA to cause damage.

True

T/F: Compton scattering is most dominant at low photon energies (1–10 keV).

False

T/F: X-rays primarily interact with the atomic nucleus to produce recoil protons.

False

Which of the following is an example of direct ionization?
A. X-rays
B. Gamma rays
C. Alpha particles
D. Neutrons

C

Indirect ionization primarily results from which type of radiation?
A. Protons
B. Alpha particles
C. Gamma rays
D. Heavy charged particles

C

Which radiation interaction involves the ejection of a loosely bound outer-shell electron?
A. Pair production
B. Photoelectric effect
C. Compton scattering
D. Nuclear spallation

C

Which interaction dominates in the 1–10 keV energy range?
A. Pair production
B. Compton scattering
C. Photoelectric effect
D. Neutron capture

C

Pair production results in:
A. An ejected K-shell electron
B. A scattered photon and electron
C. An electron and a positron
D. A recoil proton

C

Which statement about excitation is TRUE?
A. It leads to ion pair formation.
B. It removes an electron from the atom.
C. It raises an electron to a higher energy level.
D. It only occurs at energies above 1 MeV.

C

Which of the following best describes the relationship between wavelength, frequency, and velocity?
A. E = h × λ
B. c = λ × f
C. E = λ / h
D. c = h × f

B

In indirect action, the primary cause of biological damage is:
A. Alpha particles hitting DNA
B. Free radicals from water radiolysis
C. Proton bombardment of nuclei
D. Direct DNA breakage by gamma rays

B

X-rays differ from neutrons in that X-rays:
A. Interact with nuclei
B. Cause spallation
C. Interact with electrons
D. Are particulate radiation

C

Which is not involved in indirect ionization?
A. X-rays
B. Gamma rays
C. Neutrons
D. Alpha particles

D

T/F: Homologous recombination repair (HRR) is most active during the G1 phase.

False

T/F: Nonhomologous end joining (NHEJ) uses a template to repair DNA.

False

T/F: Symmetrical aberrations are generally stable and non-lethal to the cell.

True

T/F: Chromatid aberrations result from irradiation in the G1 phase.

False

T/F: Dicentric and ring aberrations are considered asymmetrical and lethal.

True

T/F: FISH allows for all chromosomes to be labeled with unique colors.

False

T/F: At low radiation doses, chromosome aberrations follow a linear-quadratic function.

True

Which of the following is a feature of homologous recombination repair (HRR)?
A. Active in all phases
B. Does not require a template
C. Highly error-prone
D. Most faithful repair mechanism

D

Which repair mechanism predominates in G1 phase?
A. HRR
B. NHEJ
C. BER
D. MMR

B

Which aberration is likely if a cell is irradiated during G1?
A. Chromatid aberration
B. Chromosome aberration
C. Fragmentation during mitosis
D. Sister chromatid exchange

B

Which of the following is not a lethal chromosomal aberration?
A. Ring
B. Dicentric
C. Symmetrical translocation
D. Anaphase bridge

C

Which technique "paints" each chromosome with a unique color?
A. G-banding
B. FISH
C. MFISH
D. MBAND

C

What distinguishes asymmetrical aberrations?
A. Balanced rearrangements
B. Often lethal and involve loss of DNA
C. Always contain two centromeres
D. Always stable

B

Which staining method uses a probe to highlight a single chromosome’s regions?
A. Giemsa
B. G-banding
C. MFISH
D. MBAND

D

Which assay is best for detecting dicentrics and rings visually?
A. FISH
B. MFISH
C. Giemsa stain
D. MBAND

C

T/F: Plating efficiency is calculated by dividing the number of colonies formed by the number of cells plated, then multiplying by 100.

True

T/F: The alpha component of the linear quadratic model represents damage that is proportional to the square of the dose.

False

T/F: The α/β ratio indicates the dose at which the linear and quadratic components of cell killing are equal.

True

T/F: Mitotic cell death is the least common form of radiation-induced cell death.

False

T/F: Senescence is a form of cell death where the cell is arrested in a non-dividing but still metabolically active state.

True

T/F: Autophagy involves the immune system attacking the irradiated cell.

False

T/F: Bystander effect describes the response of irradiated cells only, with no impact on neighboring cells.

False

What does the plating efficiency (PE) measure?
A. The number of irradiated cells
B. A cell’s ability to form a colony
C. The survival rate at high dose
D. The rate of apoptosis

B

How is survival fraction (SF) calculated?
A. Number of colonies / PE
B. Number of colonies / (cells plated × PE/100)
C. PE / number of colonies
D. (Cells plated / colonies) × 100

B

In the linear quadratic model, the alpha component represents:
A. Damage proportional to the dose
B. Damage from low LET radiation only
C. Damage at high doses
D. Lethal damage only from mitotic death

A

Which of the following best defines the α/β ratio?
A. Ratio of cell survival between low and high LET
B. Dose at which alpha and beta components contribute equally to cell killing
C. Number of alpha particles per unit dose
D. Comparison of apoptosis to senescence rate

B

Which cell death process involves the activation of self-digesting enzymes from the lysosome?
A. Apoptosis
B. Autophagy
C. Senescence
D. Bystander effect

B

Which of the following is considered the most common form of radiation-induced cell death?
A. Apoptosis
B. Mitotic cell death
C. Autophagy
D. Bystander death

B

Which type of cell death involves surrounding non-irradiated cells exhibiting damage effects?
A. Autophagy
B. Senescence
C. Bystander effect
D. Apoptosis

C

T/F: Cells in the M phase are more radiosensitive than those in the S phase.

True

T/F: Cells with mutations in genes like BRCA1, ATM, or p53 tend to be more radioresistant.

False

T/F: High linear energy transfer (LET) radiation is more damaging and harder for cells to repair.

True

T/F: The oxygen enhancement ratio (OER) indicates that hypoxic cells are more radiosensitive than aerobic cells.

False

T/F: Fractionation allows normal tissues time to repair between radiation doses, increasing their survival.

True

Which phase of the cell cycle is most radiosensitive?
A. G1
B. S
C. G0
D. M

D

Which of the following best describes the effect of low dose rate radiation?
A. Increases DNA double-strand breaks
B. Allows more time for DNA repair
C. Increases cell death
D. Enhances oxygen effect

B

Which type of radiation has the highest LET?
A. X-rays
B. Gamma rays
C. Alpha particles
D. Electrons

C

Which factor increases radiosensitivity by enhancing free radical formation?
A. Hypoxia
B. Fractionation
C. Oxygen presence
D. High dose rate

C

Which phase of the cell cycle is generally most radioresistant?
A. G1
B. M
C. G2
D. S

D

T/F: Lethal damage refers to cell damage that is irreversible and leads to cell death.

True

T/F: Potentially Lethal Damage (PLD) cannot be repaired by the cell under any circumstances.

False

T/F: Sublethal Damage (SLD) can be repaired within hours under normal conditions unless additional SLD is introduced.

True

T/F: The Elkind Experiment showed that cells can recover from sublethal radiation damage if given enough time.

True

T/F: Reoxygenation refers to the process where oxygen levels increase in tumor cells after initial radiation exposure, making them more sensitive to subsequent doses.

True

T/F: The Inverse Dose Rate Effect states that increasing the dose rate results in increased cell killing due to a slower repair process.

False

T/F: Brachytherapy involves placing radioactive sources inside the body, near the tumor, to deliver localized radiation treatment.

True

Which of the following best describes Lethal Damage in cells?
A) Damage that can be repaired over time
B) Damage that is irreversible and leads to cell death
C) Damage that can be fixed with enough oxygen
D) Damage that only affects the tumor cells

B

What does Potentially Lethal Damage (PLD) refer to?
A) Damage that cannot be repaired, resulting in immediate cell death
B) Damage that is only temporary and harmless
C) Damage that can be repaired depending on post-irradiation conditions
D) Damage that accumulates slowly and eventually leads to cancer

C

Sublethal Damage (SLD):
A) Always leads to cell death
B) Can be repaired in hours under normal conditions unless additional damage is added
C) Can never be repaired
D) Can only be repaired with radiation therapy

B

The Elkind Experiment demonstrated that:
A) Radiation causes immediate cell death with no recovery time
B) Cells can recover from sublethal damage if given time between radiation doses
C) Sublethal damage leads to irreversible cell death
D) Reoxygenation has no effect on radiation therapy

B

Which of the following is NOT one of the 4 Rs of Radiobiology?
A) Repair
B) Reassortment
C) Reoxygenation
D) Rejuvenation

D

The Dose Rate Effect (DRE) compares:
A) How cells react to acute versus chronic doses of radiation
B) How cells survive in low oxygen versus high oxygen environments
C) The difference between radiation types (X-ray vs. alpha particles)
D) The survival rates of cells depending on whether the dose is delivered quickly or over a long period

A

What effect does fractionating radiation doses have on cells?
A) It results in more cell death due to constant damage
B) It allows cells to repair damage between doses, increasing survival
C) It decreases the effectiveness of radiation therapy
D) It prevents the radiation from affecting the cancer cells

B

Which of the following best describes the Inverse Dose Rate Effect?
A) A higher dose rate results in increased cell death
B) A lower dose rate results in increased cell death because the damage is not recognized by the cell cycle checkpoints
C) A higher dose rate causes the cell to be less sensitive to radiation
D) The dose rate has no impact on cell survival

B

Brachytherapy involves:
A) Delivering radiation from outside the body, such as through X-rays
B) Using high-energy beams from outside the body to treat cancer
C) Placing radioactive sources inside or very close to the tumor
D) Delivering radiation to the entire body

C

Which of the following is true about interstitial brachytherapy?
A) It involves placing radioactive sources within body cavities
B) The radioactive source is temporary
C) The radioactive sources are implanted directly into the tumor
D) It only involves external radiation

C

T/F: The Oxygen Enhancement Ratio (OER) is always less than 1.

False

T/F: Hypoxic cells require a lower radiation dose to achieve the same biological effect as aerobic cells.

False

T/F: The oxygen fixation hypothesis states that DNA damage becomes permanent in the presence of oxygen.

True

T/F: Acute hypoxia is due to a permanent lack of blood supply in the tumor

False

T/F: As LET increases, the OER increases as well.

False

T/F: Radiation damage to DNA can be reversed if oxygen is not present and SH groups are available.

True

T/F: Chronic hypoxia results from poor oxygen diffusion to cells far from blood vessels.

True

T/F: The S phase of the cell cycle has a lower OER than the G1 phase.

False

What does the Oxygen Enhancement Ratio (OER) measure?
A. Ratio of aerobic to hypoxic doses for equal damage
B. Ratio of hypoxic to aerobic doses for equal damage
C. Radiation energy absorbed by water
D. Amount of oxygen in blood plasma

B

Which of the following best describes the Oxygen Fixation Hypothesis?
A. Oxygen prevents DNA damage
B. Oxygen allows free radical damage to be reversed
C. Oxygen "fixes" or makes DNA damage permanent
D. Oxygen enhances repair of hypoxic cells

C

Which condition is characterized by random, temporary closure of blood vessels?
A. Chronic hypoxia
B. Oxygen fixation
C. Acute hypoxia
D. Oxygen diffusion limitation

C

What happens to the OER as LET increases?
A. It increases
B. It stays constant
C. It decreases
D. It fluctuates randomly

C

Which phase of the cell cycle has the highest OER?
A. M phase
B. S phase
C. G1 phase
D. G2 phase

B

Which type of radiation typically has the lowest OER?
A. X-rays
B. Gamma rays
C. Alpha particles
D. Beta particles

C

How far can oxygen typically diffuse into tissue?
A. 10 µm
B. 35 µm
C. 70 µm
D. 150 µm

C

What allows a DNA radical to be chemically restored in hypoxic conditions?
A. Oxygen
B. Peroxy radicals
C. Sulfhydryl (SH) groups
D. Alpha particles

C

T/F: Low LET radiation causes dense ionizations along a track.

False

T/F: High LET radiation deposits energy over a short distance, resulting in dense ionizations.

True

T/F: Track average LET divides the radiation track into equal energy segments.

False

T/F: The formula for Relative Biological Effectiveness (RBE) compares a test radiation dose to a gamma or 250 keV X-ray dose that produces the same biological effect.

True

T/F: As LET increases, both RBE and OER increase.

False

T/F: RBE is affected by both radiation dose and dose rate.

True

T/F: At around 100 keV/μm, LET causes double-strand breaks in DNA due to ionizations spanning the DNA helix.

True

T/F: After the peak RBE is reached, further increases in LET result in more biological damage.

False