Model Organism’s Concept
The study of cellular mechanisms, genes, heredity and development of species were only possible due to the use of model organisms. Model organisms are non-human species whose genomes are known and which have genetic mechanisms common to a large group of related organisms. Gregor Mendel was the first to carry out studies using this type of organisms, using Pisum sativum models.
Model Organism’s Characteristics
The choice of these organisms is made taking into account their biological properties, their small size (allowing their growth in the laboratory), their short life span (allowing both the study of the organism throughout their life and the study of several generations) and ease of crossing under simple control conditions.
Commonly used Model Organisms
Because there is a diversity of complexity among species of different kingdoms, there has been a need to establish a range of model organisms to make possible the study of a wide range of biological characteristics. Among them are:
- in viruses, bacteriophage are the ones chosen. Being viruses that infect bacteria, they are used to study the physical and chemical structure of DNA, the mechanism of DNA replication and mutations;
- in prokaryotes, the bacterium Escherichia coli is used. Having no nuclear membrane or intracellular compartments, it has the advantage of being one of the few living beings capable of producing all the substances necessary for its metabolism from basic compounds;
- in the eukaryotes several models are used:
- Saccharomyces cerevisiae (yeast), is a unicellular organism that has the characteristics of being able to reproduce asexually, by division of haploid cells, or sexually, by fusion of two cells;
- Neurospora (filamentous fungus) is used because it is a haploid organism that contains eight spores in a linear arrangement, which reflect the pairing of chromosomes and the synthesis of new chromosomal filaments during meiosis;
- Arabidopsis thaliana (multicellular organism) which contains a genome of only five chromosomes and is ideal for studying the genome structure, higher plants development and comparing the development between plants and animals;
- Drosophila melanogaster (multicellular organism), which contains only four chromosomes, during its development produces body segments that resemble those of invertebrates and vertebrates;
- Caenorhabditis elegans (multicellular organism) is used for developmental studies because its embryonic cells give rise to progenitor cells that will form specific regions already known and;
- Mus musculus (multicellular organism) has been (and continues to be) of great importance in the study of the immune system since it is very similar to that of the human organism.
Despite the diversity of organisms, all tend to present similar genomes and genetic mechanisms, making it possible that studies on model organisms can be partially extrapolated to all other species.
References:
Griffiths A.J.F., Wessler S.R., Lewontin R.C., Gelbart W.M., Suzuki D.T., Miller J.H. (2004). An Introduction to Genetic Analysis (8ª edição). W. H. Freeman, New York.
