1) Which one of the following statements concerning the interaction of photons with matter is CORRECT?
A. The probability of the photoelectric effect decreases with the atomic number of the absorber.
B. The predominant interaction of 10 keV photons with soft tissue is the Compton process.
C. In the Compton process, the energy of the scattered photon is less than that of the incident photon.
D. Pair production occurs for photons with energies less than 1.02 MeV.
E. There is only partial absorption of the energy of the incident photon in the photoelectric effect.
2) Which one of the following is a radiolysis product of water responsible for 2/3-3/4 of the molecular damage caused by the indirect action of ionizing radiation?
A. eaq
B. 1O2
C. OH-
D. OH•
E. O2-
3) The approximate minimum photon energy required to cause ionization is:
A. 10-25 eV
B. 100-250 eV
C. 1-2.5 keV
D. 10-25 keV
E. 100-250 keV
4) Which of the following statements concerning free radicals is INCORRECT? Free radicals:
A. have longer half-lives than ion radicals
B. can diffuse and therefore extend damage beyond the primary radiation path
C. play an important role in the oxygen effect
D. tend to have half-lives on the order of seconds
E. are central to the indirect effect of radiation
5) Which of the following X-ray interactions with matter is most important for producing high-contrast diagnostic radiographs?
A. Compton process
B. pair production
C. photoelectric effect
D. nuclear disintegration
E. coherent scattering
6) Which of the following pairs of photon energy and predominant atomic interaction at that energy is correct?
A. 1 keV – pair production
B. 50 keV – triplet production
C. 100 keV – Compton process
D. 2 MeV – photoelectric effect
7) High LET radiations:
A. include 250 kVp X-rays, 200 MeV protons and 1.1 MV γ-rays
B. produce much higher yields of OH radicals than do either X-rays or γ-rays
C. produce higher levels of clustered lesions in DNA than X-rays
D. are components of solar flares but not of cosmic rays
E. produce less dense ionization tracks than γ-rays
8) SF2 of p53 (TP53) wild-type cells is most closely correlated with the:
A. level of γ-H2AX 0.5 hour after irradiation
B. level of γ-H2AX present 24 hours after irradiation
C. acetylation of H2AZ on lysine 4
D. rate of DNA single-strand break repair
E. rate of thymine glycol repair
9) Which of the following types of DNA damage is not caused by X-rays?
A. double-strand breaks
B. thymine glycols
C. clustered base lesions
D. oxidized bases
E. pyrimidine dimers
10) A clustered lesion:
A. results from the creation of multiple double-strand breaks within a particular exon of a gene following exposure to a high LET radiation
B. involves the formation of several DNA lesions within a highly localized region of DNA
C. occurs more frequently as the LET of the radiation decreases
D. represents the repair of multiple lesions within a gene
E. results from transcription-coupled DNA repair
11) Which one of the following assays would be the most appropriate to use for quantitative measurement of DNA double-strand breaks in cells immediately after exposure to ionizing radiation?
A. alkaline elution
B. western blotting
C. neutral comet assay
D. PCR
12) Double-strand DNA breaks caused by ionizing radiation trigger the transcription of DNA damage response genes. Which of the following proteins is a transcriptional transactivator?
A. p21 (CDKN1A)
B. p53 (TP53)
C. ATM
D. CHK1 (CHEK1)
E. TRAIL (TNFSF10)
13) Which of the following molecular events most immediately follows the creation of a double-strand DNA break?
A. destabilization of the mitochondrial outer membrane
B. inactivation of the CDC25 phosphatases
C. phosphorylation of CHK1 (CHEK1)
D. activation of p21 (CDKN1A) transcription
E. phosphorylation of histone H2AX
14) Which of the following statements is FALSE?
A. DNA repair by homologous recombination occurs preferentially in the G1 phase of the cell cycle.
B. Non-homologous end joining is an error-prone repair pathway that involves DNA-PKcs (PRKDC)-associated repair of DNA double-strand breaks.
C. The DNA repair proteins MRE11, NBS1 (NBN) and RAD50, localize at nuclear foci corresponding to presumed sites of DNA damage following exposure to DNA-damaging agents.
D. A defect in nucleotide excision repair is the basis for the hereditary disorder xeroderma pigmentosum, and can lead to increased rates of skin cancer.
E. Following the production of DNA double-strand breaks, ATM is converted from an inactive dimer to an active monomer form.
15) Which of the following proteins is most closely associated with homologous recombinational repair of radiation-induced DNA double-strand breaks?
A. RAD51
B. XPG (ERCC5)
C. DNA-PKcs (PRKDC)
D. CHK1 (CHEK1)
E. TFIIH
16) An agent that inhibits non-homologous end joining (NHEJ) repair of radiation-induced DNA double-strand breaks might be expected to do all of the following, EXCEPT:
A. affect the immune response
B. sensitize cells to low-dose-rate irradiation
C. decrease the tolerance dose for most normal tissues during fractionated radiotherapy
D. increase cellular radioresistance
E. inhibit sublethal damage recovery
17) All of the following proteins are involved in non-homologous end-joining of DNA double-strand breaks, EXCEPT:
A. XRCC4
B. RAD52
C. Artemis (DCLRE1C)
D. KU70 (XRCC6)/KU80 (XRCC5)
E. DNA ligase IV (LIG4)
18) A mutation in which of the following genes is LEAST likely to cause an increase in sensitivity to ionizing radiation:
A. NBS1(NBN)
B. BRCA1
C. ATM
D. MRE11
E. XPC
19) Which of the following statements concerning DNA repair is CORRECT?
A. Single-strand annealing is an error-free process.
B. Cells deficient in nucleotide excision repair tend to display hypersensitivity to ionizing radiation.
C. A person with LIG4 syndrome is radiation sensitive.
D. Mismatch repair involves the action of a DNA glycosylase and an AP endonuclease.
E. People with Fanconi anemia exhibit normal sensitivity to DNA cross-linking agents.
20) Two of the main proteins involved in mismatch repair are:
A. MSH2/MLH1
B. DNA ligase IV (LIG4)/XRCC4
C. KU70 (XRCC6)/KU80 (XRCC5)
D. XPA/XPG (ERCC5)
E. DNA-PKcs (PRKDC)/Artemis
21) Which of the following best describes the action of an exonuclease enzyme?
A. seals breaks in a DNA strand
B. required for DNA replication
C. produces nicks within intact DNA strands
D. controls mRNA synthesis
E. removes nucleotides from the ends of DNA strands
22) The protein deficient in individuals diagnosed with Nijmegen breakage syndrome plays an important role in:
A. base excision repair
B. nucleotide exicision repair
C. translesion DNA synthesis
D. DNA helicase activities
E. homologous recombinational repair
23) Base excision repair (BER):
A. when defective, may increase mutation rate, but usually does not alter cell survival after X-irradiation
B. when defective, increases cell sensitivity to both UV and ionizing radiation
C. involves the XP and CS genes
D. acts on DNA lesions such as pyrimidine dimers, single-strand breaks and bulky adducts
E. is defective in patients with Li-Fraumeni Syndrome
