A MULTIVARIATE QUANTITATIVE-GENETIC ANALYSIS OF BEHAVIORAL-DEVELOPMENT IN MICE

The present experiment attempted a behavior-genetic dissection of earl y behavioral development in laboratory mice. To this end, we used a fu ll, replicated diallel cross to uncover the genetical architecture as well as the multivariate genetic structure underlying early behavioral ontogeny. A number of standard sensorimotor tests were administer-ed on postnatal Days 3, 5, 8, 10, 13, 17, and 22 to a total of 622 pups f rom 120 litters (4-6 pups per litter)from a four times replicated comp lete diallel cross between five inbred mouse strains. The first day on which an animal showed adult performance was taken as its score on th at test. MANOVA did not show any effects of the pup's sex on the speed of development. Hayman's analysis of variance for diallel tables indi cated no or only weak additive-genetic effects. Dominance was absent i n almost all cases, except for the auricular startle response, where w eak directional dominance for fast development was Sound. These result s are in accordance with an evolutionary past of directional selection for well-canalized development. Factor analyses of the phenotypic and additive-genetic con-elation matrices indicate that at least two fact ors are necessary to describe the behavioral variation. (C) 1998 John Wiley & Sons, Inc.