Drinking Water and Health, Volume 9 Selected Issues in Risk Assessment (1989) / Chapter Skim
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Glossary
Glossary
Pages 79-88
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From page 79... ...
ADDUCT A chemical addition product. For example, when the mutagenic alkylating agent ethyl methanesulfonate reacts with DNA, any of the normal bases in DNA (i.e., adenine, thymine, guanine, and cytosine)
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From page 80... ...
8-AZAGUANINE An analogue of the normal DNA and RNA purine base guanine; selection for resistance to the toxic effects of 8-azaguanine is the basis for several mutation-detection systems. BASELINE ADDUCTS Endogenous adducts found on DNA from "unexposed" organisms or individuals.
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From page 81... ...
COVALENT BINDING A stable chemical bond formed between two atoms in which electrons are shared by both. CROSS-LINKING The joining of two DNA strands or a DNA strand with a protein strand by a bifunctional or polyfunctional alkylating agent.
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From page 82... ...
ENZYMATIC REPAIR SYSTEMS Cellular enzymes capable of recognizing and repairing altered DNA templates. EXCISION REPAIR The enzymatic removal from DNA of an altered base or nucleotide, followed by resynthesis and rejoining of the DNA.
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From page 83... ...
HPRT Hypoxanthine-guanine phosphoribosyl transferase (also called HGPRT) ; an enzyme involved in the utilization of the purine bases hypoxanthine and guanine in mammalian cells (there are related enzymes in submammalian species; mutants that lack HPRT are resistant to the toxic effects of the guanine analogues 8-azaguanine and 6-thioguanine, which can therefore be used to select HPRT mutants and form the basis of several mutation-detection systems.
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From page 84... ...
NONINVASIVE In reference to analytical techniques requiring a test specimen, not involving injury to the subject. NUCLEOPHILIC SITE Within a chemical structure, a region with a negative charge that attracts positively charged chemical groups, or donates electrons.
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From page 85... ...
RISK ASSESSMENT Includes four components: hazard identification, exposure assessment, dose-response assessment, and characterization of risk at projected levels and patterns of exposure. Qualitative risk assessment involves only the first two, and sometimes a limited amount of the third, whereas quantitative estimates of human risk include all four components and involve more uncertainties and less consensus about the most appropriate animal models, data sets, and conversion factors to use in calculation.
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From page 86... ...
; catalyzes the phosphorylation of thymidine to thymidine monophosphate; mutants that lack TK are resistant to the toxic effects of several thymidine analogues, including bromodeoxyuridine and trifluorothymidine; selection of these drug-resistant mutants provides the basis of several mutation-detection systems, most notably in mammalian cells. TIME-WEIGHTED AVERAGE An average exposure concentration calculated from intermittent samplings of exposure concentrations.
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From page 87... ...
TRANSCRIPTION The synthesis of RNA on a DNA template in such a way that the sequence of nucleotides in the RNA is the complement of the sequence of nucleotides in DNA. VALIDATION The process by which the consistency of a particular test is determined; the concordance of results of a test in question and previously established tests for a representative sample of chemicals is evaluated.
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Key Terms
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