Anatomy, physiological features, genetics and genetic alterations, breeding and strain differences relevant to the choice of the modeldImpact of 3Rs

While primary and utmost effort should be given to develop and use nonanimal alternatives, the other 2Rs are essential: when conducting experiments, the final decision very often is not between animal and nonanimal; instead, it is which animal? Which strain? Thus, success and validity of research depends on the selection of the most appropriate animal model to address key scientific questions.