ABSTRACT
It is often thought that, since individual mice of inbred strains are essentially the same and that normal gross anatomy and histology would be the same for all mice, only a few mutants from a new strain need to be examined and that controls are not necessary. Similarly, there are those who believe that only the obviously affected organs or specific organs, such as the liver, kidney, and lungs of the mutation, need to be examined and that the whole mouse need not be looked at. Characterization of a new mutation using these limited approaches can lead to incomplete and erroneous descriptions of the phenotype. The only way to provide complete characterization of the phenotypic effects of a new mutation is to do a thorough, systematic evaluation of sufficient mutant and control mice. This can even be done when only a small breeding colony of the animals can be maintained, if mice are collected at specific ages, and specimens are accumulated over time.
