a1 Laboratory of Genetics University of Wisconsin, Madison, Wisconsin 53706, U.S.A.
a2 Department of Meat and Animal Science University of Wisconsin, Madison, Wisconsin 53706, U.S.A.
Covariance between direct and maternal genetic effects on body weight in random-bred ICR mice at 2 through 10 weeks of age was estimated from cross-fostering experiments. The covariance contributes only a few percent of phenotypic variance at 2 weeks, but increases to 10–15% at later ages. Nearly all estimates are positive. We suggest that genes active during later parts of growth affect maternal performance more than those active during early growth, causing increased covariance at later ages. A model of combined genetic and persistent environmental effects on maternal performance is presented. Persistent effects of genetic or environmental variation in recent ancestors can influence covariance between relatives and response to selection.
(Received August 21 1984)
(Revised January 23 1985)