Bone length and muscle weight in mice subjected to genetic selection for the relative length of the tibia and radius

Mice which had undergone 5 generations of selection for high and low values of the tibia length/radius length ratio were compared with unselected controls at 10 weeks of age. The ratio responded to selection in both directions. The length of the radius was increased in the low line while the response in the high line was due to an increase in the length of the tibia and a small but statistically insignificant decrease in radius length. High and low line mice were heavier than the controls. The responses of the tibia and femur and of the radius and humerus were generally similar, suggesting the existence of an association between the genetic control of the lengths of the bones of a limb. There were also correlated responses in the weight of the tibialis anterior, biceps brachii and sternomastoid, and there is some evidence to suggest that the weight of a muscle may be influenced by the length of a bone to which it is attached.