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Questions and Answers
Which type of cell division results in two genetically identical daughter cells?
Which type of cell division results in two genetically identical daughter cells?
- Meiosis
- G1 phase
- Mitosis (correct)
- G2 phase
What is the defining feature of the S portion of the cell cycle?
What is the defining feature of the S portion of the cell cycle?
- Chromosome segregation
- DNA synthesis (correct)
- Cell division
- Metabolic processes
During which phase of the cell cycle is DNA synthesized but other metabolic processes are taking place?
During which phase of the cell cycle is DNA synthesized but other metabolic processes are taking place?
- M phase
- G1 phase
- G2 phase (correct)
- S phase
Which period of the cell cycle is not characterized by DNA synthesis?
Which period of the cell cycle is not characterized by DNA synthesis?
During which phases of the cell cycle are cells most radio-sensitive?
During which phases of the cell cycle are cells most radio-sensitive?
What characterizes the cell cycle time for stem cells in certain tissues?
What characterizes the cell cycle time for stem cells in certain tissues?
Which of the following is true about the adaptive response to radiation?
Which of the following is true about the adaptive response to radiation?
How does oxygen tension affect cell sensitivity to low LET radiation?
How does oxygen tension affect cell sensitivity to low LET radiation?
What is the purpose of radioprotective drugs?
What is the purpose of radioprotective drugs?
What are chemical agents that reduce cell response to radiation called?
What are chemical agents that reduce cell response to radiation called?
Why do females tend to be slightly more radioresistant than males?
Why do females tend to be slightly more radioresistant than males?
According to age, which group is the most radio-sensitive?
According to age, which group is the most radio-sensitive?
What is the most important site of damage in a cell due to radiation?
What is the most important site of damage in a cell due to radiation?
Which type of radiation usually causes isolated DNA damage?
Which type of radiation usually causes isolated DNA damage?
What is more complex and harder to repair than isolated damage?
What is more complex and harder to repair than isolated damage?
What type of DNA damage is typically repaired using base-excision repair mechanisms?
What type of DNA damage is typically repaired using base-excision repair mechanisms?
What are the possible outcomes of cell irradiation mentioned in the text?
What are the possible outcomes of cell irradiation mentioned in the text?
What type of effects are suffered by individuals during their lifetime due to radiation?
What type of effects are suffered by individuals during their lifetime due to radiation?
Which type of effects from radiation exposure have a probability of occurrence that increases with dose but no relation to severity?
Which type of effects from radiation exposure have a probability of occurrence that increases with dose but no relation to severity?
What type of radiation-induced effects are highly predictable, with a threshold dose that triggers a dose-dependent response?
What type of radiation-induced effects are highly predictable, with a threshold dose that triggers a dose-dependent response?
What is represented by the shoulder on the cell survival curve?
What is represented by the shoulder on the cell survival curve?
Which type of radiation can result in more complex DNA damage, making repair more difficult?
Which type of radiation can result in more complex DNA damage, making repair more difficult?
When is cell death most sensitive to radiation?
When is cell death most sensitive to radiation?
What may low doses of radiation initiate that reduces the consequences of subsequent exposures?
What may low doses of radiation initiate that reduces the consequences of subsequent exposures?
Which type of radiation can be shielded with Plexiglas?
Which type of radiation can be shielded with Plexiglas?
What is the term used to describe the amount of energy imparted locally in a target by radiation?
What is the term used to describe the amount of energy imparted locally in a target by radiation?
Which radiation type has the highest ability to penetrate materials?
Which radiation type has the highest ability to penetrate materials?
Which effect of radiation involves a transfer of energy from the radiation directly to the target molecule, typically DNA?
Which effect of radiation involves a transfer of energy from the radiation directly to the target molecule, typically DNA?
What can lead to tissue damage, with an estimated two-thirds of the biological damage caused by low LET radiation being due to indirect action?
What can lead to tissue damage, with an estimated two-thirds of the biological damage caused by low LET radiation being due to indirect action?
What is believed to be particularly important in producing biological damage by the indirect action of x-rays?
What is believed to be particularly important in producing biological damage by the indirect action of x-rays?
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Study Notes
- Cell death for stem cells and other cells with high division capacity is referred to as reproductive death.
- Apoptosis is a process by which an organism induces cells that may pose a threat to commit suicide.
- Apoptosis can be induced by radiation, which is generally a good thing since dead cells don't become cancerous.
- Failure of apoptosis can increase the probability of malfunctioning cancerous cells proliferating if radiation damages the genes that induce apoptosis.
- Radiation is classified into two main categories: non-ionizing and ionizing.
- Ionizing radiation can be further divided into directly ionizing (charged particles) and indirectly ionizing (neutral particles) radiation.
- Ionizing radiation has the ability to penetrate and transfer energy to the material it is penetrating. The term "Linear Energy Transfer" (LET) is used to describe the amount of energy imparted locally in a target.
- Alpha particles have a high LET, low penetrating ability, and can be shielded by a piece of paper.
- Beta particles have a low LET and can only penetrate low-density materials, they can be shielded with Plexiglas.
- X-rays and gamma rays have a low LET and the highest ability to penetrate materials. High-density materials are needed to shield against these waves.
- X-rays interact with atoms through the photoelectric effect, Compton scattering, or pair production, resulting in the production of free radicals that can damage DNA.
- Direct radiation effects involve a transfer of energy from the radiation directly to the target molecule, typically DNA. These effects are most important for high LET radiation.
- Indirect radiation effects occur when radiation produces free radicals that react with the target molecule, typically DNA. These effects are most important for low LET radiation.
- Indirect radiation effects can be modified by chemical sensitizers or radiation protectors.
- Ionizing radiation interacts with water, leading to the production of free radicals that can damage DNA and other molecules.
- The presence of an excess of oxygen during irradiation of cells allows the formation of additional free radicals.
- Much of the damage caused by radiation is believed to be due to oxygen containing radicals, ions, and peroxides collectively known as reactive oxygen species (ROS).
- The hydroxyl radicals are believed to be particularly important in producing biological damage by the indirect action of x rays.
- Radiation leads to tissue damage, with an estimated two-thirds of the biological damage caused by low LET radiation being due to indirect action.
- Radiation-induced malignancies can occur if the radiation directly affects somatic cells and alters the DNA (and hence the chromosomes) as a result.
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