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rad bio chapter 7
| Question | Answer |
|---|---|
| branch of biology concerned with the effects of ionizing radiation on living systems | radiation biology |
| damages living systems by ionizing atoms comprising the atoms compromising the molecular structure of these systems | ionizing radiation |
| Biologic damage begins with the ionization produced by various types of radiation, such as | x-ray, gamma rays, alpha & beta particles, & protons |
| Amount of energy that is transferred by the radiation to an object along a unit length | Linear Energy Transfer (LET) |
| unit of LET | kiloelectron volts |
| low linear energy transfer radiation? | gamma rays, x-rays, electrons |
| high linear energy transfer radiation? | alpha particles, ions of heavy nuclei, low energy neutrons, charged particle products of neutrons & atoms |
| T/F High linear energy transfer causes more biologic damage than low. | True (1000x more) |
| The capability of radiation with different LETs to produce a biologic reaction | Relative Biologic Effectiveness (RBE) |
| oxygen creates tissue to be more radiosensitive | oxygen effect |
| Oxygen Enhancement Ratio (OER) equation | Radiation dose required to produce a response in an oxygen deprived environment / radiation dose required to cause biologic response of O2 |
| when any kind of biologic damage happens in an oxygenated environment the damage is permanent/fixed | oxygen fixation hypothesis |
| what does oxygen produce? | free radical |
| Any visible radiation-induced injuries of living systems at the cellular or organic level always begin with damage at what level? | the molecular level |
| If somatic cells are affected by radiation what may happen? | entire body processes may be disrupted |
| If germ cells are damaged by radiation what may happen? | the damage may be passed on to future generations in the form of genetic mutations |
| 2 classifications of ionizing radiation interaction | direct action (DNA) and indirect action (H2O) |
| Radiation has interacted directly with the molecule and ionized it/alternating the molecule (High LET) | direct action |
| when an x-ray photon interacts with a water molecule; forms free radicals: molecules that are highly reactive (disrupt bonds in other molecules); low LET | indirect action |
| ionization of water molecules | radiolysis of water |
| highly reactive molecule | hydroxyl radical |
| what does radiolysis of water produce? | Undesirable chemical reactions & biologic damage; Production of cell damaging substances; Organic free radical formation |
| a loss or change in nitrogenous bases of a DNA strand (base change) | mutation |
| chemical bond formed between 2 atoms that should not have a bond | covalent cross links (inter-strand cross links) |
| when chromosome is irradiated in interphase (before DNA synthesis) | chromosome aberrations |
| when chromatid is irradiated (AFTER DNA synthesis) | chromatid aberrations |
| chromosomes repaired itself | restitution |
| what percentage of chromosomes fix themselves? | 95% |
| chromosome was not able to be fixed; part of chromosome has been deleted/lost | deletion |
| what does deletion create? | acentric fragment (iso-chromatid) |
| broken end rearrangement without visible damage to the chromatids | reciprocal translocation |
| A master, or key, molecule that maintains normal cell function is believed to be present in every cell | Target Theory |
| cellular effects of radiation | 1. Instant death 2. Reproductive death (10 rads) 3. Apoptosis or programmed cell death (interphase death) 4. Mitotic or genetic death 5. Mitotic delay (.01 gray) 6. Interference with function 7. Chromosome breakage |
| T/F Immature cells or undifferentiated & reproducing rapidly are more radiosensitive | TRUE |
| what cells are considered very radiosensitive that are reproducing? | basal cells of skin, blood cells (lymphocytes & erythrocytes), interstitial crypt cells, & reproductive (germ) cells |
| what are considered radiosensitive cells that are highly specialized & non-reproducing? | brain cells, muscle cells, and nerve cells |
| Studied the effects of ionizing radiation on testicular cells | Law of Bergonie and Tribondeau (1906) |
| what are the effects of ionizing radiation on blood cells? | Hematologic depression Depletion of immature blood cells Repopulation |
| which is considered to be the MOST radiosensitive blood cell? | lymphocyte |
| how many grays can cause bone marrow to not repopulate? | above 10 grays |
| how many grays can cause male sterility? | 5-6 grays |
| how many grays can depress the sperm population & result in mutations? | 0.1 grays |
| how many grays can cause temporary sterilization? | 2 grays |
Created by:
gnteumac
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