genetic engineering

In 1953 he discovered the phenomenon called restriction, certain phages (bacterial viruses) that infect E. coli could develop in certain strains of this bacterium, but they could not in others (are said to be "restricted" in certain strains).

In the late 60's, Werner Arber, Basel, discover restriction enzymes responsible for this phenomenon: the strain of bacteria produces restrictive endonucleases (restriction enzymes, or restrictases ") that cleave the phage DNA into another strain grown different.

Those first restriction enzymes were unspecific as to the DNA site where they would cut, but in 1970 Hamilton O. Smith, in Baltimore, he discovers a new type of restriction enzyme absolutely specific: able to recognize a specific DNA sequence of a few base pairs, and cut in both strands at specific sites.

1972, Mertz and Davis added to a mixture of DNA from different backgrounds an enzyme DNA ligase, seeking reparations for phosphodiester bonds. And this made them realize that they could form the basis for the production of recombinant molecules in vitro, with genetic material from different species.

But this recombinant DNA, generated in the test tube, is inert, no more than a hybrid macromolecule itself does nothing. If we want to do something recombinant DNA, must be inserted into living cells that are able to express their genetic information.

This brings us to the idea and what is genetic engineering: in vitro formation of new combinations of genetic material through the insertion of a DNA genetic interest in a vehicle (vector), so that after its introduction in a host organism's DNA hybrid (recombinant) can multiply, spread, and eventually expression.