1. The percentage of x-ray damage to biologic material
mediated by free radicals is closest to _______.
2. X-ray–produced chromosomal aberrations, such as
dicentrics and rings, are generated as a consequence of which of the following
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
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
D. Symmetric translocations
5. Which phase of the cell cycle is most variable in length?
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
Answers and Feedback