LWBK1006-07 LWW-Govindan-Review November 22, 2011 13:54
CHAPTER 7 PRINCIPLES OF
RADIATION ONCOLOGY
HAK CHOY•NATHAN KIMDIRECTIONS Each of the numbered items below is followed by lettered answers. Select the
ONE lettered answer that is BEST in each case unless instructed otherwise.QUESTIONS
Question 7.1. Which of the following describes the specific pathways for the repair of
double-stranded DNA breaks?
A. The repair may be by homologous recombination (HR) or nonho-
mologous end-joining (NHEJ) pathway.
B. The HR repair pathway functions by degrading the single strand at
each side of the break and then annealing the two ends.
C. The NHEJ pathway functions by replicating the missing genetic infor-
mation from the homologous DNA template.
D. NHEJ is a minor component of mechanism for repair of double-
stranded DNA breaks in mammalian cells.Question 7.2. Which of the following is NOT true about ionizing events in tissues caused
by x-rays?
A. Radiation dose describes the quantity of energy deposited per mass
of tissue.
B. The fast electrons produced by high-energy x-ray photons can dam-
age deoxyribonucleic acid (DNA) by a direct action.
C. The relative biological effectiveness (RBE) describes the ratio of doses
required to yield an equivalent biologic event.
D. Indirect action of ionizing radiation where hydroxyl radicals damage
target tissues is not commonly seen.Question 7.3. Which of the following statements describes the DNA damage/repair
process associated with ionizing radiation?
A. Single-stranded breaks of the DNA are thought to represent the lethal
event.
B. All of the radiation-induced, double-stranded breaks are rejoined in
cells within 2 hours.
C. In mammalian cells, choice of repair can be biased by phase of the
cell cycle and by abundance of repetitive DNA.
D. Nonhomologous end-joining (NHEJ) is effective in rejoining DNA
double strand break because it is an error free process.Corresponding Chapter inCancer: Principles & Practice of Oncology,Ninth Edition: 27 (Radiation Oncology).85