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19 Cards in this Set
- Front
- Back
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Epigenetic mechanisms that can promote cancer (REVIEW)
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- Binding to receptors on cell surface, in cells
- Interfering with gene activity: Histone protein modification, Methylation of DNA, Hormonal modification (incrs/decrs cell division) |
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What is Radiation?
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Movement of energetic particles or wave through a medium or through space (no medium)
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How does cell ionization occur?
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when electron is knocked off an ACTG base. Caused if radiation is energetic enough to do this.
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Long waves are ________________
Short waves are high-frequency and ________________ |
Non-ionizing
Ionizing |
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What is an alpha particle?
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energetic particle that could get into a cell and break DNA strand
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How do we measure radioactivity?
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Bequerel (Bq) = decay of 1 nucleus per second; #decays/time
Gray (Gy) = 1 joule/kg ; amt of energy deposited in a medium by ionizing radiation per unit mass. Measures absorbed dose. Sievert (Sv) = measures equivalent and effective doses |
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3 ways of describing radiation absorbed by tissue
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Absorbed Dose
Equivalent Dose Effective Dose |
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Absorbed Dose
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Amt energy deposited in a medium by ionizing radiation per unit mass.
Measured in Grays Not helpful in estimating health risk b/c does not account for different btwn particl and wave sources of ionizing energy or sensitivity of different organ/tissues |
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Equivalent Dose or "biologically equivalent dose"
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Takes into account impact of different types of radiation on biological tissues - i.e. diff tissues more radiosensitive, like rapidly growing tissue
Measured in Sieverts (grays * radiation weighting factor) |
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Effective Dose or "relative biological effectiveness" (RBE) or "Q" or "weighting factor"
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Accounts for whether energy deposited in tissue came from alpha, beta, x-ray particle.
Used to convert a directly measurable physical quantity (absorbed dose, Gy) into an estimate of biological effect (equivalent dose). Accounts for differing radiosensitivity of tissues Weighting factors: photon, electron is RBE = 1 Proton is RBE = 2 Neutron (depends on energey) is RBE = 5-20 Alpha particle is RBE = 20 Grays * radiation weighting factor *weighting factor for tissue type |
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DNA-Radiation Interactions - how does ionization occur?
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Radiation interacts with matter and causes the formation of ion pairs
(positively charged atom + negatively charged electron) |
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Direct vs Indirect Ionization
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Direct - radiation track deposits energy in DNA
Indirect - radiation track deposits energy in hydrogen or oxygen atoms very close to DNA and H or O radicals damage DNA. |
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DNA Repair and Radiation
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Depends on size of rays
Gamma, X-rays - low-density track of damage. Easy to repair Beta particles - high density track of damage, clusters of damage caused, harder to repair |
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Protections for Radiation
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OSHA standards exist for radiation exposures at work
General pop'n - gets background radiation exposure - International Commission on Radiological Protection (2007) |
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Health Risks of Radiation
Deterministic |
Deterministic: single, brief exposure - could be burns, acute "radiation sickness". The more Grays, the higher the risk of dying. Can cause bone marrow suppression b/c of cell death in rapidly dividing tissues
Ex. Hiroshima & Nagasaki - whole body doses |
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Health Risks of Radiation
Stochastic |
Probabilistic effects, usually refers to cancer.
No threshold mutagenic, carcinogenic effects Ex: thyroid cancer following Chernobyl disaster |
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Radon
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Environmental, "natural" cause of lung CA. Ores in ground generate radon, which emits alpha particles.
Enters buildings thru basement/cracks in foundation Inhaled |
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Preventing Radon Exposure
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Measure
Interevene if home concentraion 4 pCi/L Reduce exposure -general ventilation, avoid time in basement, seal foundation |
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Why does radon cause lung CA and not skin CA?
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Alpha particles are easily stopped, so they can't get through skin. But if inhaled, they can easily cross thin cellular membranes.
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