46 Questions
Which of the following best defines 'reproductive integrity' in the context of cell survival curves?
The ability of cells to divide indefinitely and produce a large number of progeny
What is the dominant mechanism of cell death in most cells?
Mitotic death
What is the mean lethal dose for loss of proliferative capacity in proliferating cells?
Usually less than 2 Gy
Which of the following is a characteristic of apoptosis?
Condensation of chromatin
What is the role of autophagy in irradiated cells?
To restore or maintain cellular homeostasis
Which factor influences the bystander effect?
Cell communication via gap junctions
What is the relationship between chromosomal aberrations and cell survival?
Quantitative correlation observed
Which type of radiation displays a straight line curve, approximating exponential cell killing?
α-particles
What is the equation for the single-target/single-hit model?
SF = exp(-αD)
What is the equation for the multitarget model?
SF = exp(-αD - βD^2)
What does the α/β ratio represent in the linear-quadratic model?
The dose at which linear and quadratic contributions to the survival curve are equal
Which phase of the cell cycle is the most resistant to radiation?
DNA synthesis phase (S)
What is the cell cycle duration for resting mouse skin stem cells?
200 hours
Which phase of the cell cycle has the second peak of resistance to radiation?
G1
Which repair mechanism is more faithful and occurs after replication in the S phase?
Homologous recombinational repair (after replication in S phase, more faithful)
Which of the following is true about the effective dose-survival curve in multifraction radiotherapy?
The curve is an exponential function with increasing dose
What is the relationship between D0 and D10 in the effective dose-survival curve?
D10 = 2.3 × D0
What is the total dose required to give a 90% chance of tumor cure in a tumor containing 10^8 cells, based on the given effective dose-response curve?
62.1 Gy
If clonogenic cells undergo three cell doublings during treatment, what total dose would be required to achieve the same probability of tumor control as in the previous example?
69.9 Gy
Which phase of the cell cycle shows the greatest resistance to radiation-induced cell killing?
S phase
What is the purpose of the G2 checkpoint genes?
To initiate and complete repairs before mitosis
Which synchronization technique is applicable to monolayer cultures only?
Mitotic Harvest Technique
What is the characteristic response of Chinese hamster cells to X-rays during the cell cycle?
Surviving fraction peaks in late S phase
True or false: Cell survival curves illustrate the relationship between radiation dose and cell survival proportion.
True
True or false: Reproductive death refers to the ability of a cell to divide indefinitely and generate a large clone of cells.
False
True or false: The mean lethal dose for loss of proliferative capacity in proliferating cells is usually less than 2 Gy.
True
True or false: The plating efficiency measures the percentage of cells forming colonies.
True
True or false: The surviving fraction is calculated by dividing the number of colonies counted by the product of the number of cells seeded and the plating efficiency.
True
True or false: The linear-quadratic model describes cell killing with two components, one proportional to dose (αD) and the other proportional to the square of the dose (βD^2).
True
True or false: The single-target/single-hit model can adequately explain most cell survival data from mammalian cells.
False
True or false: The D0 of the effective dose-survival curve is the dose required to reduce the fraction of surviving cells to 37%.
True
True or false: The total dose for nine decades of cell killing is 62.1 Gy.
True
True or false: Three cell doublings would increase the cell number by 8.
True
True or false: If the D0 is 2.2 Gy and the total dose is 40 Gy, the number of cells remaining is 10^9 × 10^8.
False
True or false: Cyclins and Cyclin-Dependent Kinases (CDKs) are regulatory proteins controlling cell cycle transitions?
True
True or false: Dysregulation of the cell cycle can lead to diseases, including cancer?
True
True or false: Hydroxyurea is a drug widely used for drug-induced synchronization of cell cultures?
True
True or false: The radiosensitivity of mammalian cells peaks in late S phase during the cell cycle?
True
True or false: Hydroxyurea induces synchronization in S phase cells for at least 4 hours?
True
True or false: Mouse jejunum's epithelial lining is a self-renewal tissue?
True
True or false: Radiosensitivity is highest in late S phase?
False
True or false: The oxygen effect ratio (OER) is lower for cells in G1 compared to cells in S?
True
The α/β values indicate the radiosensitivity or radioresistance of cells.
True
The bystander effect refers to the induction of biological effects in irradiated cells.
False
Apoptosis and mitotic cell death are mutually exclusive processes.
False
Autophagy is always a protective mechanism for cells to survive and generate nutrients and energy.
False
Test your knowledge on inherited human syndromes associated with X-rays, including Ataxia-telangiectasia (AT) and the genes involved in DNA double-strand break repair. Discover the link between these syndromes, their symptoms, and the increased risk of cancer.
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