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62 Cards in this Set
- Front
- Back
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Radiobiology:
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The branch of biology that studies the effect of radiation on living things and their biological systems
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What is Radiation?
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The emission of energy through space or matter.
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Particulate Radiation
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Does not leave the body, it's absorbed into the tissues, heavier, charged particles, part of the atom.
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Electromagnetic Radiation
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Visible light, x-rays, microwaves, radiowaves, no mass and no charge particle.
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Photon
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packet of energy which travels at 3 x 10 raised 8th m/sec in free space.
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Particulate Radiation
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Directly ionizing radiation, charged particles ( gamma and beta)
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Electromagnetic Radiation
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Indirectly ionizing radiation; photons (y & x) and neurons
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Gamma Rays
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Come directly from the nucleus
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X-Rays
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Come directly from the electrons
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4 Indirectly ionizing radiation
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Go!
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(1) Coherent or Classical Scattering
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About 5% is coherent or classical scattering.
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Photoelectric Effect
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Interaction with a low energy photon and an inner shell (k,l,m) results in the ejection of the electron. Therefore, disappearance of the incident photon and release of characteristic X-rays.
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Compton Effect
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Interaction with a photon in the medium energy range and a loosely bound orbital electron. Results in the ejection of the electron and a deflection of the incident photon minus the binding energy of the orbital electron.
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Pair Production (Does not happen very often)
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The photon hits the outer electron and the electron (e-) becomes positive. This newly created positron will find free e- very fast and create energy.
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Electrons produced in the body via Photoelectric effect or the Compton effect go on and cause ionizations and excitation eventually losing all of their energy.
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These ionizations and excitations can effect biologically sensitive molecules in living tissues. This creates free radical!
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Free Radical
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Damage to biologically sensitive molecules is primarily from free radicals which are produced by the interaction of the secondary electrons
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What is a free radical?
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Similar to an ion but has no charge, and has an unpaired electron which makes it very reactive. (Atoms are happy when their shells are full.)
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Free Radicals are looking for another electron.
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It is an atom looking for a more stable electron structure by either the gain or the loss of an electron.
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Dosimetry
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The science of dose measurement.
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Rad
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100 ergs/g
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Gray
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100 Rads = 1 J/kg
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Both units are absorbed dose
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Radiation absorbed by a person is described as a dose.
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Directly Ionizing
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Charged particles such as alpha, beta, protons, heavy fragments. They frequently break chemical bonds and ionize atoms with no intermediary.
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Indirectly Ionizing
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Photons and neutrons. Cause the secondary production of charged particles which then break chemical bonds and ionize atom.
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Spurs and blobs of secondary ionizations occur along the radiation track.
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Deals with DNA
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LET
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Linear Energy Transfer: THe average density of energy loss along a path of the particle of the particle. Measured as keV/um. Greater LET means shorter distance in tissue.
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Directly ionizing radiation has a high LET, indirectly ionizing has a lower LET (long space) . THE EXCEPTION TO THS IS THE NEUTRON.
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Radans = deposit all of its energy in a very small space.
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Ionization of water = Photon will interact with water inside your body.
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Since most biological tissues are about 80% water, water plays a role in the production of biological damage. This is very important with indirectly ionizing radiation.
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Neutrons vs. Photons
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X-rays interact with orbital electrons. Neutrons interact with the atomic nucleus. Both are indirectly ionizing radiations but neutrons are more densely ionizing because they have a mass. Which means they produce more of a ionizations per unit length. Because of this fact, the possibility of direct ionization increases.
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Cellular Structure
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Go over in your anatomy textbook!
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Chromosomes
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Thread like structures in the nucleus composed of DNA which codes for genes and other materials that control their expression. Chromosomes are normally contained witting the nucleus; The chromosomes contain 6 feet of tightly wound DNA. Each cell in the human body contains the entire human genome, make up of 6 million base pairs. Each gene codes for specific molecule, usually a protein.
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Chromatid
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One half of a chromosome
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Each gene codes
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For 1 specific amino acid.
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Watsona & Crick
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Published the paper on the structure of DNA in 1953. They are accredited with discovering the structure of DNA molecule.
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Rosalyn Franklin
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Obtained the first X-Ray crystalography image of the DNA. She died at the age of 37 and never got to speak up about the work she did.
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Somatic Cells
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Diploid differentiated cells composing of body tissues of multicellular plants and animals. Somatic cells contain the full complement of chromosomes, which in humans is 46 or 23 pairs. 23 are from the mother, and the other 23 are from the father.
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Genetic Cells
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Reproductive Cells with a single complement of chromosomes (sperm or egg.) Also, known as a haploid cells or germ cells.
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Cell Cycle (Interphase) contains S,G1,G2
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S phase: Synthesis of DNA, Chromosomes are replicated. Replicated chromosomes are identical to the original.
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G1 Phase:
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Follows mitosis; Resting phase for S phase.
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G2 Phase:
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Follows S phase. Resting period before mitosis.
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Interphase:
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The normal stage of the cell cycle. The period which the cell spends most of its life cycle. Genetic material is not visible. However, it is replicated during the synthetic phase.
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Mitosis
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When a cell divides, the chromosomes replicates and the duplicates are distributed to each daughter cell; hence, each daughter cell has 46 chromosomes and is, from a genetic perspective, quantitively and qualitatively identical to the parent cell.
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Prophase
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Chromatic condenses. Chromosomes become visible. Each chromosome is made up two duplicate chromatids attached by a centromere. Centrioles move apart, spindle fibers can be seen between the two centrioles and the nucleolus disappears. The nuclear membrane disappears marking the end of prophase.
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Metaphase
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Chromosomes line up at the equator of the cell.
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Anaphase:
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Chromatid pairs separate to opposite poles. Single chromosomes appear to be dragged by their centromeres.
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Telophase
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Chromosomes have reached the opposite poles. Spindles disappear. Nuclear membranes reform. Chromosomes diffuse. Cytokinesis, division of the cytoplasm begins.
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Common Aneuplodiy
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Involve chromosome 13, 18, or 21. 21 results in down syndrome
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Aneuplodies etc.
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May involve the X and Y chromosome and may actually result in as many as three or four of these sex chromosomes.
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A disturbance in the # of chromosomes can also be associated with
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Cancer
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Cancer:
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A disturbance in the routine, orderly process by which a normal cell duplicates and divides, causing the cell to duplicate and divide more frequently than neighboring cells. The growth of cancer cells is limited only by the supply of nutrients.
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Cancer etc
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Cancer cells are immortal and they shut off when they should. They have an unlimited number of life cycles which results in out of control growth.
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Variations in Chromosome Structure:
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Chromosomes may deviate from their normal state in many ways.
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An alteration from the norm is called an
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aberration or mutation . The association of chromosomal deviations with cancer are also many and varied with respect to tissue and cell types and the time they occur.
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Deletion:
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An aberration in which a segment of a chromosome is missing; this may be a segment large enough to be detected under the microscope (macrodeletion) or so small that only sophisticated methods can detect it (microdeletion.)
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Frameshift:
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The impact of an insertion or deletion in the protein coding region of the gene. Because codons consist of groups of three basic bases, subtracting or adding a base or bases changes the coding of all the codons that follow.
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THE BIG HAT SAT
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If we insert a letter in the second word, the meaning of everything that comes after it changes.
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THE BAI GHA TSAT
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A similar effect would happen by deleting a letter. This shift in the "reading frame" in a gene would cause the gene to code for a different sequence of amino acids in its protein product. HUGE AFFECT
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Duplication
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An aberration in which a segment of a chromosome is repeated and thus is present in more then one copy within a chromosome.
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Rearranging:
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An aberration in which a segment of a chromosome is shifted within the same chromosome. Sometimes turned upside-down (inversion.)
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Transfered to another chromosom, the latter kind of rearrangement is
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Translocation
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Translocation
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An aberration in which a chromosome segment is transfered to another chromosome or different chromosome.
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Aberration types: Ionization radiation causes all of this!
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All of these may occur in combination with each other, a common occurrence in various forms of cancer.
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