Genetic selection disrupts stability of mouse brain weight development.

Fuller Brain Weight Selection lines are well differentiated for 42-day brain weight and a high degree of genetic homogeneity for trait-relevant genes is indicated. Using these lines, random bred descendants of the foundation population and an inbred line, biometrical analysis of brain growth from birth to 23 days was attempted. While strain means differ as expected, within and between litter variances for genetically heterogeneous mice were typically no greater than for more genetically homogeneous selected lines. Possible explanations involving gestational age, intra-uterine and postnatal competition and ontogenetic buffering are discussed.