Section 2 Cellular Response to Radiation

2. X-ray–produced chromosomal aberrations, such as dicentrics and rings, are generated as a consequence of which of the following events?
A. A single chromosomal break interacting with itself
B. Interaction of two separate chromosomal breaks
C. High-dose events caused by a single electron
D. Misreplication events

3. Cell killing by X-rays correlates best with which of the following measures?
A. Damage to DNA bases
B. The initial number of DNA double-strand breaks
C. The final number of DNA double-strand breaks
D. The number of thymine dimers

4. Chromosome changes induced by radiation include __________. (Select any that apply.)
A. Acentric fragments
B. Centric fragments
C. Inversions
D. Symmetric translocations
E. Dicentrics

5. Which phase of the cell cycle is most variable in length?
A. G1
B. G2
C. M
D. S

6. If an asynchronous population of cells is exposed to a single x-ray dose of 10 Gy, the surviving cells are partly synchronized because __________.
A. Radiation block occurs in the G₁ phase.
B. Radiation block occurs in the S phase.
C. Most survivors are in the G₂ phase.
D. Most survivors are in the late S phase.

7. The shoulder in cell survival curves is MOST pronounced when cells are irradiated with __________.
A. 1-MeV neutrons.
B. 2-MeV alpha particles.
C. 5-MeV electrons.
D. 100-MeV pi mesons.

8. For a given total dose of x-rays, a protracted exposure at a low dose rate is less effective in killing mammalian cells than an acute exposure at a high dose rate. This occurs primarily because __________.
A. Fewer free radicals are produced.
B. The mitotic cell cycle is shortened.
C. Cell division occurs during exposure.
D. Ion pairs recombine during extended exposure.
E. Repair of sublethal damage occurs during exposure