Genes as gerontological variables: uniform genotypes

Genetic conceptualizations and procedures have become integral to the condu ct of research across the spectrum of life sciences, including gerontology, even when genetics is not the focus of inquiry. Among the research tools t hus provided, one of the most basic is that of inbred strains. A close appr oximation to genetic uniformity is achieved by a sufficient number of succe ssive generations of matings of relatives, and, once this near-uniformity i s attained, the members of an inbred strain constitute a reference group re latively stable over time and available to diverse investigators. Different inbred strains possess different genotypes, so that numerous distinctive r eference groups are available. The stability of these groups enhances prosp ects of replication-testing, and makes possible the focused accumulation of pertinent data. Phenotypic differences among strains identify particular g roups that can be most appropriate for particular subsequent research objec tives (and also provide ipso facto evidence of genetic influence on the phe notype). The very substantial advantages of the uniform genotypes provided by inbred strains (and by their F-1 offspring) are purchased at the cost of limited generalizability of results and constraints on assessment of co-va riation among variables. Uniform genotypes are, thus, not a tool for all pu rposes but must be seen as a powerful basic tool within an abundant genetic tool-kit. Particular research purposes will require use of more than one t ool from the kit. (C) 1999 Elsevier Science Inc. All rights reserved.