Conventional breeding, especially of crops, livestock and fish, focuses principally on increased productivity, increased resistance to diseases and pests, and enhanced quality with respect to nutrition and food processing.
Advances in cellular genetics and cell biology methods in the 1960s contributed to the so-called ‘green revolution’ that significantly increased varieties of staple food crops containing traits for higher yield and resistance to diseases and pests in a number of both developed and developing countries.
A key driver of the green revolution was to improve the potential to provide sufficient food for all.
The intensification and expansion of agriculture brought about by these methods and agricultural systems have, however, also resulted in new forms of health and environmental risks through, for example, increased use of agrochemicals and intensified cultivation resulting in soil erosion.
Various transformation methods are used to transfer recombinant DNA into recipient species to produce a GMO.
For plants, these include transformation mediated by Agrobacterium tumefaciens (a common soil bacterium that contains genetic elements for infection of plants) and biolistics shooting recombinant DNA placed on microparticles into recipient cells.
The methods used in the transformation of various animal species include microinjection, electroporation and germ-line cells.
The success rate of transformations in animals tends to be lower than in plants, and to vary from species to species, thus requiring the use of many animals.
Genetic modification is often faster than conventional breeding techniques, as stable expression of a trait is achieved using far fewer breeding generations.
It also allows a more precise alteration of an organism than conventional methods of breeding, as it enables the selection and transfer of a specific gene of interest.
However, with the present technology, in many cases it leads to random insertion in the host genome, and consequently may have unintended developmental or physiological effects.
However, such effects can also occur in conventional breeding and the selection process used in modern biotechnology aims to eliminate such unintended effects to establish a stable and beneficial trait.