It is worth first clarifying that a model organism is an organism used as a model in biological research aimed at studying its properties, its reactions to certain stimuli, and transferring the results to the properties and reactions of other organisms. Often the use of model organisms becomes an inevitable necessity when it comes to research on humans, which is impossible due to ethical or technical reasons. In this case, model organisms cover the whole range of organisms existing on the planet. There are several criteria by which an organism can be referred to as a model object. First of all, it is a comprehensive study by independent scientists. Secondly, it is easy and safe to use in laboratory conditions. Thirdly, it is a short period of generation or self-reproduction. Fourthly, it is the possibility of genetic mutations. Finally, the model organism must have a fully sequenced and decoded genome. The most famous of the model organisms are Escherichia coli, Chlamydomonas, Drosophila, Poplar, and Rice, as well as Mouse, Pig, and Monkey.
The use of the model greatly simplifies the study of organisms with similar properties, as it reduces the economic and knowledge-intensive costs of study and also allows for the reproduction of results due to multiple attempts. It should be emphasised, however, that the transfer of properties of one organism to another is not always lawful, and the results of such action are mainly of probabilistic nature. In order to bring this probability as close as possible to 100%, an organism that claims to be a model must be studied as carefully as possible.
Traditionally, it is believed that the use of model organisms in functional genomics is reduced to the study of prokaryotes and lower eukaryotes, whose metabolism is thoroughly studied. Nevertheless, the scientific community is increasingly resorting to the study of diseases characteristic of the human body through the use of higher eukaryotic forms, such as the grey rat. Table 1 shows the difference in genomic characteristics for the three model organisms. Each of them has found its application for human activity, and while some specialists use prokaryotic plasmids of E. coli, others try to find out the genetic pattern of diabetes by studying R. norvegicus.