Biological Effects of Radiation Flashcards
7 cards from real CHP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Biological Effects of Radiation flashcards as text
Radiation-induced apoptosis is predominantly triggered by:
Answer: p53-dependent pathways activated by DNA double-strand breaks
DNA double-strand breaks activate ATM kinase, which phosphorylates and stabilizes p53, leading to transcription of pro-apoptotic genes such as Bax and PUMA in the intrinsic apoptotic pathway.
The 'inverse dose-rate effect' observed with some low-LET radiations means:
Answer: At certain low dose rates, cell killing per unit dose can be GREATER than at high dose rates due to cells accumulating in sensitive cell cycle phases
The inverse dose-rate effect occurs when continuous low-dose-rate irradiation allows cells to redistribute into and accumulate in radiosensitive cell cycle phases (G2/M), paradoxically increasing cell kill per unit dose.
Which term describes the ability of a given dose of radiation to cause cancer relative to a standard reference radiation?
Answer: Radiation weighting factor (wR)
The radiation weighting factor (wR) in the ICRP system reflects the relative biological effectiveness of different radiation types for stochastic effects and is used to calculate equivalent dose in Sieverts.
The phenomenon where heavily irradiated cells transfer damaging signals to distant unirradiated cells via serum or culture medium is called:
Answer: The bystander effect mediated by soluble factors
Soluble-factor-mediated bystander effects occur when cytokines, reactive oxygen species, or other molecules released by irradiated cells damage distant unirradiated cells, demonstrating that direct irradiation is not required.
Radiation-induced fibrosis in late-responding normal tissues is primarily driven by:
Answer: Persistent TGF-β signaling leading to chronic fibroblast activation and collagen deposition
TGF-β (transforming growth factor-beta) is persistently upregulated after irradiation and drives fibroblast-to-myofibroblast differentiation, collagen overproduction, and progressive tissue fibrosis.
In assessing radiation risk for in utero exposures, the period of GREATEST sensitivity for teratogenic effects (organ malformation) is:
Answer: Major organogenesis (2–8 weeks post-conception)
The period of major organogenesis (approximately weeks 2–8 post-conception) is most sensitive for radiation-induced teratogenesis because organ primordia are differentiating rapidly and errors produce structural malformations.
The excess relative risk (ERR) model for radiation-induced cancer implies that:
Answer: The radiation-induced excess cancer risk is proportional to the baseline (spontaneous) cancer risk
The ERR model expresses radiation risk as a multiplicative factor on the background cancer rate, meaning populations with higher baseline rates will experience a proportionally larger absolute excess from the same dose.