To test whether lung structure in mice is genetically determined, two inbred strains of mice and their F1 offspring of the same age and gender were studied. Body size and lung size were measured, and various morphometric parameters were calculated. Each parameter was analyzed to elucidate the effects of dam, sire, both, or none by a genetic analytical method. The two inbred lines differed in lung and body size as well as in morphometric parameters. These parameters were found to be under genetic control by sire, dam, both, or none. From the data of reciprocal crossing, it appears that there is a maternal effect on the following parameters: body weight, fresh lung weight, fixed lung volume/fresh lung weight, specific lung volume, alveolar wall proportion, mean alveolar wall thickness, and mean linear intercept. Through a more detailed genetic analysis, it was found that specific lung volume in one F1 offspring showed an additive effect. On the other hand, the following parameters indicated heterotic effects (an increase or decrease in dimension compared to the parents with many possibly favorable) in one or both F1 offspring: body weight, fresh lung weight, fixed lung volume/fresh lung weight, specific lung volume, alveolar wall proportion, mean alveolar wall thickness, mean linear intercept, mean chord length of alveoli, mean chord length of alveolar ducts, alveolar surface area, and alveolar surface area to lung volume ratio. These findings indicate that genetic effects are important factors in normal lung development.
