Experimental Studies on the Genetics of Spontaneous Leukemia in Mice*

The genetic constitution of an individual largely governs its morphological development and its response to both internal and external stimuli. The inherited character may be expressed regardless of the nongenetic or environmental influences; or the nongenetic influences may completely suppress the genetic tendencies. Neither, in a large majority of the cases, is completely suppressed by the other. For a satisfactory study of one, it is desirable that the other be kept constant. But biological material is never constant and environmental changes are always present although they may not be readily determined. Changes in genetic constitution also occur universally and, while progeny may resemble their parents to all outward appearances, special breeding tests will show the existence of certain minor variations and such variations can be accentuated through suitable breeding procedures. The extensive investigations herein reported were designed to evaluate the importance of genetic constitution in the development of spontaneous leukemia in mice.