Biotechnology Basics – What is a Model Organism?

What is a model organism?

A model organism is any plant, animal or microorganism that allows us to study fundamental questions in biology that may be hard to study directly in complex organisms like humans.

What are some characteristics of a model organism?

The tiny fruit fly D. melanogaster is a powerful tool for studying genetics!  ©Edvotek 2014
The tiny fruit fly D. melanogaster is a powerful tool for studying genetics! ©Edvotek 2014

In general, model organisms have fast generation time, breed in large numbers and have a sequenced genome. Many model organisms are relatively simple and inexpensive to use,so they are widely available for use in the classroom. Common model organisms include the zebrafish, the mouse, the rat, the fruit fly D. melanogaster, the nematode C. elegans, the budding yeast, the bacteria E. coli and Arabidopsis, just to name a few!

What can a fruit fly really tell me about human biology?

Human biology is extremely complex. There’s a lot going on in our bodies that we just don’t understand. Performing experiments in humans, however, is highly unethical. We are still able to make insights into human development and disease by studying similar genes in model organisms.

Mendel discovered the rules of heredity using the humble pea plant. ©Edvotek 2014
Mendel discovered the rules of heredity using the humble pea plant. ©Edvotek 2014

Many of the basic principles of biology that were first identified in model organisms have later been demonstrated in humans. For example, Gregor Mendel used pea plants to establish that genes have different forms, or alleles, and that these alleles segregate independently from one another. Building on this work, Thomas Hunt Morgan used the fruit fly to illustrate the linkage of a gene to a particular chromosomal location. Today, we know that most human traits observe these rules of inheritance.

Analyze DNA sequences using BLAST! © Edvotek 2014
Analyze DNA sequences using BLAST! © Edvotek 2014

Modern technology has allowed scientists to determine the sequence the genome of many model organisms. DNA sequence comparison software like BLAST has allowed scientists to identify genes that are similar to those that are important for human health and development. Scientists can learn more about these genes by studying their function in a model organism. For instance, about 75% of the genes that cause disease in humans have homologs in D. melanogaster. For example, the fly model of Alzheimer’s disease has provided new information on the disease, which has allowed scientists to identify novel targets for treatment.

Interested in learning more about model organisms?  Come to our training sessions at the NSTA Conferences on Science Education!  

In this exciting workshop, you will learn how to use the nematode C. elegans to explore the effects of mutations on alcohol metabolism using a simple locomotion assay.  Ethanol has been used since ancient times for its intoxicating effects. This common recreational drug acts as a central nervous system depressant. At low blood alcohol concentrations (BAC), ethanol produces stimulating, euphoric effects. As the BAC increases, brain function is progressively reduced, leading to slurred speech, poor motor control, and sedation. At BACs over 0.4%, effects include reduced heart rate, unconsciousness, and death. Relative intoxication depends upon variables such as age, weight, sex, tolerance, and ingestion of food. Additionally, single base-pair changes in a person’s DNA can reduce the activity of enzymes that break down ethanol, leading to higher BACs that persist for longer periods of time.

C. elegans is a common model organism  ©Edvotek 2014
C. elegans can be used to study alcohol metabolism. ©Edvotek 2014

Performing experiments that characterize the human response to ethanol can be unethical and, in some situations, dangerous. In order to study the effects of mutations on ethanol metabolism, we will use the model organism C. elegans. The nematode is an ideal system for this study because mutations have been identified that render them insensitive to the effects of ethanol. In this inquiry-based experiment, you will expose wild-type and alcohol resistant C. elegans to different concentrations of ethanol. Next, you will compare the behavior of the two strains and record the effects. Finally, we will utilize critical thinking and statistics skills to interpret the data.

If you can’t make to one of our workshops, click here for a PDF download of the presentation.