What Is a Model Organism?

Over the last century, research on a small number of organisms has played a pivotal role in advancing our understanding of numerous biological processes. This is because many aspects of biology are similar in most or all organisms, but it is frequently much easier to study a particular aspect in one organism than in others. These much-studied organisms are commonly referred to as model organisms, because each has one or more characteristics that make it suitable for laboratory study. The most popular model organisms have strong advantages for experimental research, such as rapid development with short life cycles, small adult size, ready availability, and tractability, and become even more useful when many other scientists work on them. A large amount of information can then be derived from these organisms, providing valuable data for the analysis of normal human development; gene regulation, genetic diseases, and evolutionary processes.

Mammalian Models

Mammals share many basic biological functions, such as the regulation of cell division, the development of organ systems, and immune response.

The mouse is the closest mammalian model organism to humans. The gene sequences that code for numerous proteins responsible for carrying out vital biological processes in both the human and the mouse share a high degree of similarity. Therefore, the mouse has already proven extremely useful in development, genetic, and immunology studies. Elucidation of the mouse genomic sequence will also provide a system for studying and understanding human disease, as well as a mechanism for investigating new treatment strategies in ways that cannot be done in humans.

The rat is a principal model organism to link function to genes. The large number of inbred rat models and the vast amount of data available for the rat provide important strengths for the study of human health and disease. In some instances, specific aspects of human disease are duplicated well only in the rat, making these animals a unique resource for studying and identifying genetic pathways relevant to human disease. The rat is also a model of choice for many physiological studies related to cardiac and vascular function, pulmonary circulation, metabolism, neurological control, age- and gender-related differences, and studies related to hypertension and signal transduction.