What are the limitations or disadvantages of using model organisms?

Question

What are the limitations or disadvantages of using model organisms?

Answer 1

Model organisms are usually chosen for reasons of convenience. Depending on the type of research performed, common characteristics tend to include:

1. Small Size

2. Rapid Generation Time

3. Easy Upkeep

4. Easy Experimentation: in genetics (my field), and ideal model organism is transformable, there are techniques to isolate nucleic acids, etc.

5. High Volume of Background Information

Plus a few others depending on your area of research (i.e. an ecologist will look at different characteristics and criteria that a geneticist).

A model is chosen for specific purposes and the choice depends on what your are trying to find out. Often when making the choice you must make compromises that will limit the extrapolation of your findings to other species.



The general disadvantages are:

1. Your model may not be truly representative of similar species. Example- Plant geneticists use Arabidopsis thaliana as a model, however as plants go Arabidopsis has an abnormally small genome, and comparatively little repetitive DNA.

2. Genetic Variance. When doing certain types of studies your data might vary because there is natural genetic variance in a population. This can be overcome by using inbred lines that have low genetic variability which can make your results more consistent.

3. Background Knowledge. It's not always possible to use a model that has extensive background information. Today for example many genomes have been sequenced. If you use a model that has not been sequenced you are limited as to what types of experiments you can do (or you are forced to do extensive preliminary experiments).

4. Transfer of Methodology. Techniques used in your model may only work in your model and will not work in other species. This also includes applications like statistics.  

5. Lack of Methodology. You may wish to perform certain types of experiments, however it may not be possible. For example efficient targeted gene removal is currently not possible in plants. To properly characterize a gene you should look at a null mutant, however this is not always possible.