title: Study design and sample sizes for a lacI transgenic mouse mutation assay.
abstract: Design features that adjust and account for excess variation in a transgenic mouse mutation assay based on a lacI target transgene from E. coli are considered. These features include proper identification of plate, packaging reaction, and animal identifier codes throughout the experimental and analysis phases of the study, "blocking" of exposed and unexposed animals when preparing and plating multiple packaging reactions from the same genomic DNA sample, separating sectored mutant plaques and complete mutant plaques before performing any quantitative analyses, and testing for sources of excess variation attributable to features of the experimental protocol--such as plate-to-plate (within packaging reactions), packaging reaction-to-packaging reaction (within animals), and animal-to-animal (within study). Control and ethylnitrosourea-treated animal data are presented from a fully designed study in the lacI assay. The study design incorporates many of these experimental principles. Statistical methods to identify excess variability are noted, and the designed study data are used to illustrate the types of variability encountered in practice. A standard statistical test for two-sample testing is highlighted, from which recommendations are made for sample size selection in future studies.
authors.affiliation: Department of Statistics, University of South Carolina, Columbia 29208, USA.
authors.forename: W W
authors.initials: WW
authors.lastname: Piegorsch
authors.forename: B H
authors.initials: BH
authors.lastname: Margolin
authors.forename: M D
authors.initials: MD
authors.lastname: Shelby
authors.forename: A
authors.initials: A
authors.lastname: Johnson
authors.forename: J E
authors.initials: JE
authors.lastname: French
authors.forename: R W
authors.initials: RW
authors.lastname: Tennant
authors.forename: K R
authors.initials: KR
authors.lastname: Tindall
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D016010:Binomial Distribution; D004247:DNA / Q000187:drug effects; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D005038:Ethylnitrosourea / Q000633:toxicity*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D056968:Lac Repressors; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic / Q000235:genetics*; D009010:Monte Carlo Method; D016296:Mutagenesis / Q000187:drug effects / Q000235:genetics; D009152:Mutagenicity Tests / Q000379:methods*; D011897:Random Allocation; D012097:Repressor Proteins / Q000235:genetics; D012107:Research Design; D018401:Sample Size
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D056968:Lac Repressors; C539064:LacI protein, E coli; D012097:Repressor Proteins; D004247:DNA; D005038:Ethylnitrosourea