Sexual dimorphism and direct and maternal genetic effects on body weight in mice.

Genetic and phenotypic parameters for three-, six- and eight-week body weight and for weight gain between three and six weeks of age were estimated from data collected over 14 generations in a randombred control population. Genetic parameters were also estimated for sexual dimorphism in body weight and gain. Heritability estimates were substantial for body weight at all ages and for body weight gain. Additive maternal variances were also large. Estimates of the covariance between direct and maternal genetic effects were negative and substantial for three- and six-week weights and gain. Also the covariance between maternal effects on weaning weight and direct genetic effects on six- and eight-week weights were negative. These results indicate a consistent antagonism between maternal and direct genetic effects in this population.The analysis of sexual dimorphism yielded estimates of 0.87±.09 and 0.71±.14 for the correlation between additive direct effects on males and females for six-week weight and body weight gain respectively. Corresponding heritability estimates were 0.07±.09 and 0.11±.09. Heritability estimates for sexual dimorphism in three- and eight-week weights were negative.