Basic research using model organisms has taught us much of what we know about biology. This research has identified the fundamental properties of how cells grow and divide, how inheritance works, and how organisms store and use energy. By studying model organisms, scientists are learning more about how the brain functions and what drives behaviors like eating, sleeping, sex and even aggression. This foundation of knowledge has led to new methods for maintaining health and for diagnosing and treating disease in humans.
What is a model?
The word model has many meanings, but in science, a model is a simplified system that is accessible and easily manipulated. A model organism is an animal, plant or microbe that can be used to study certain biological processes.
Why use model organisms?
Research on bacteria, yeast, insects, worms, fish, rodents and plants has shown that the basic operating principles are nearly the same in all living things. So a finding made in fruit flies can shed light on a biological process in people.
Model organisms generally grow quickly, are relatively simple and inexpensive to work with, and are widely available for use in experiments.
Why is model organism research useful for studying diseases?
The natural course of a disease in a human may take dozens of years. Simple organisms that can develop a disease or some of its symptoms make it possible for researchers to learn about the disease faster—in a period of months to a few years. That would be nearly impossible, and often unethical, to do in humans.
When scientists discover that a particular gene is associated with a disease in humans, one of the first things they typically do is find out what that gene does in a model organism. This often provides important clues for understanding the cause of a disease and for developing potential diagnostic tests and treatments.
How has model organism research impacted human health?
Here are a few of the many examples:
- Yeast studies sorted out the orderly sequence of events, called the cell cycle, in which a cell duplicates its contents and divides into two. This information has benefited millions of people, since many drugs used to treat cancer act by interfering with the cell cycle.
- Experiments performed with yeast have also clarified how genes are turned on or off. This knowledge explains how cells that contain the same genes can be so different from one another, which has advanced understanding of both normal developmental processes and diseases that occur when genes are turned on or off at the wrong time or in the wrong cell.
- Studies in fruit flies and tiny worms taught scientists key aspects of how fertilized eggs develop into complex organisms. In the course of these studies, researchers made unanticipated discoveries, such as learning that genetically controlled cell death plays a critical role in cancer and other diseases.
- Research with bacteria, viruses and yeast has revealed how all living things pass on their genes to offspring through copying DNA and fixing mistakes that get made during the copying process.
- Laboratory rats have been used for many decades to test drugs. In addition, much of what we know about cancer-causing molecules was learned through basic research with rats.
- Mice can be genetically engineered to serve as models of Lou Gehrig's disease and many other human illnesses.
- Insects such as fruit flies and honeybees are important models for learning how genes and the environment interact to affect behavior.
- Studies with fruit flies, bread mold, bacteria and mice have defined the basic rules of circadian clocks, which drive daily biological rhythms, and revealed connections between these clocks and sleep deprivation, obesity, diabetes, depression and other human health conditions.
- Research in worms has yielded important information about aging. This research is very difficult to do in people and other organisms that have long life spans.
- Model organism research has produced many powerful tools used by scientists all over the world. Examples include RNA interference, DNA chips and genome-wide scanning methods. These tools are now being used in human health studies.
What more can model organism research tell us?
Scientists still do not have a good understanding of biological complexity, in which many molecular networks operate in synchrony inside our bodies. Researchers are mapping these networks in bacteria, yeast and other model organisms, and those studies will be instructive for creating working models of how cells, organs and tissues function in people.
Model organisms can also help reveal changes at the molecular level that are associated with diseases and identify diseases that are related to one another even though they initially may not appear to be. If there is already a drug to treat one of the diseases, scientists can then explore whether it might work for the related ones, as well.
What about computer models?
Computers serve as virtual laboratories where scientists can do experiments that are very difficult to do in real life. For example, in computer-simulated environments, researchers can introduce into a virtual human population a virus with certain characteristics and then watch it spread. They can also test what might happen as a result of vaccination, school closure or other interventions.
Because the models are so complex, high-performance computers are needed to generate many computer simulations. Often, these computers run for weeks at a time, generating millions of different possible outcomes.
No single set of results or single computer model can predict exactly what will happen, so researchers often ask the same questions in different kinds of models. When different models yield similar results, scientists have more confidence in the predictions.
Can computer models replace animal models in research?
Even though computer models are limited by what is already known about a process or disease, they are valuable tools that scientists can use to suggest ideas that then can be tested in real organisms. The information that results from the experiments continually enhances the computer modeling approaches. Thus, the two types of models go hand in hand, relying on each other to advance our understanding of health.
NIGMS is a part of the National Institutes of Health that supports basic research to increase our understanding of biological processes and lay the foundation for advances in disease diagnosis, treatment and prevention. For more information on the Institute's research and training programs, visit http://www.nigms.nih.gov.
Content revised November 2012