Reverse Genetics
One of the main aims of genetics and polymorphism studies is associating a phenotype with the corresponding genotype. Reverse genetics, on the other hand, starts with the gene, transform the species with it and studies the resulting phenotypes. The two disciplines are separated by several decades and a change in context. Reverse genetics is the paradigm shift that stemmed the industry of biotechnology in the late 70's.
Initially, genetics fell mainly into the field of biology, given that it did not have any particular use for other sectors. Geneticists succeeded in identifying new mutant phenotypes and in establishing certain links between these mutants (complementation, epistasis, etc.). They were therefore able to develop coherent theoretical systems in which genes could be organized into biological pathways with a hierarchy of interactions. This method was certainly perfect when observing a phenotype was simple to track, and very limited methods could be done directly to nucleic acids to alter heredity (chemical or physical methods). It is this approach to genetics that was adopted by key figures such as Johann Gregor Mendel in the nineteenth century with the pea, Thomas H. Morgan in the early twentieth with drosophila and, more recently, Barbara McClintock with maize.
Developments in molecular biology then enabled the identification of genes and the translation of this “genetic logic” into a molecular map, the first stage of which was the identification of the mutated genes responsible for phenotypes. Progress in molecular biology also enabled the identification of a large number of genes whose function was still unknown. One of the best ways of identifying the function of a gene is to study the consequences of its inactivation or insertion, and it is this which led to the concept of reverse genetics. Gene insertion has been performed by introduction of DNA in cells an random insertion but gene targeting needed a way of selectively mutating a given gene. In many cases (mostly in yeasts and mammal systems), the total or partial inactivation (“knockout”) of a selected gene was carried out by homologous recombination.
Today, the genome sequencing of numerous species has led to a new interest in reverse genetics: thousands of genes have been identified, but their function is not yet known. To understand their function they must firstly be inactivated and then modified, mutated, replaced or inhibited in order to study the phenotypes resulting from these modifications.
There is a growing need in biotechnology for effective tools for rational reverse genetics, or, more specifically, for effective tools for genetic intervention.
