## A model organism must meet several requirements

As this is a book about genetics, we can start the discussion about the properties of a “good” model organism using Mendel's hybridization experiments as an example. It illustrates that when choosing an organism for the study of a given phenomenon, it is necessary to be very careful and at the same time to be lucky. The fact that Mendel's results did not find a response in the scientific community at the time of their publication was due, among other things, to the fact that he tried to prove that his rules also apply to another plant. His choice of plant to prove his theory was the hawkweed (Hieracium), which although studied by botanists in the 19thCentury, had one feature that disqualified it as a model organism for the study of the foundations of heredity: this genus of plants reproduces apomictically. This means that an egg can also form an embryo without fusing with the male gamete. Of course, Mendel could not obtain the same results for the hawkweed as for the pea, which reproduces sexually and thus his genius had to wait for recognition for 20 years when his results were “re-discovered”.

How can we avoid a similar mistake that happened to Mendel? Here is a list a few properties that a good model organism should meet (Table 20.1).

Table 1. Properties of a good model organism.

Property | Explanation
Size | For the statistical evaluation of experiments, it is necessary to have data on a large number of individuals.
Availability and easy maintenance in the laboratory | The financial and technical means of maintaining the organism in the laboratory should be as low as possible.
Short reproduction cycle | It is ideal to do as many experiments as possible in the shortest possible time, e.g. enabling their easy repeatability
Possibility of use for the study of a wide spectrum of phenomena | It is advantageous if the organism is not useful for study of a single phenomenon but can be used to address several problems.
Easy observability and possibility of quantification of the studied property | "Hidden" properties require more sophisticated and therefore more financially/technically demanding methods.
Techniques enabling targeted (e.g. genetic) manipulations | Advantageous for genetic analysis of studied properties.
Genome size | Too large a genome complicates genetic manipulation and interpretation of results.
Generalisation of the results | Advantageous in the case of phenomena with a more general occurrence; it may not apply if we are interested in a property specific to a given type of organism.

Now, we know what it takes to be a good model organism, we can introduce a few examples.