Transgenics or transgenic organisms or genetically modified organisms (GMOs) are organisms which contain foreign gene(s) or extra copies of an endogenous gene incorporated in their genetic make up.
These are genetically engineered organisms created by transfer of additional gene(s) into their genome. These foreign genes are suitably integrated into the host genome and are also expressed in transgenic organisms. The combined applications of recombinant DXA technology, gene transfer and tissue culture (in plants) are required for transgenics production.
Transgenics microbes are made viable by microbial cloning. Transgenic microbes are used for large scale production of human insulin, human growth hormone somatotropin, vaccines such as Hepatitis B vaccine etc. One landmark step in transgenic microbe is the creation of Superbug by Indiaborn American scientist Dr. Anand Chakarbarty. lie introduced plasmids from different strains of Pseudomonas into a single cell to create a strain of bacteria to be used in the break down/ consume hydrocarbons. These bugs can be used to clean the oceans of oil spills.
Transgenic plants are created by transferring useful foreign genes to a host plant culture (tissue culture). Then the genetically modified cultures are grown into transgenic plants. The gene transfer can be done either by Agrobacterium mediated gene transfer or by direct gene transfer (described earlier). Transgenic plants are developed with insect and disease resistance capacities, increased nutritional values, increased storage quality, production of edible vaccines etc.
Transgenic cotton plant known as Bt cotton is developed by transfer of insect resistance gene from Bacillus thurngiensis so that Bt cotton is resistant to bollworm. The gene from the bacterium enables the plant to synthesize insecticidal ciystal protein.
A transgenic variety of tomato called Flavour-saver tomato has a much longer and more flavorful shelf-life than normal tomatoes. In this transgenic tomato, the longer shelf life is achieved by reducing the amount of cell wall degrading enzyme polygalacturonase responsible for fruit softening.
Transgenic Golden Rice is developed Swiss biotechnologist, ingo potrykus and his team. It contains genes for phytoene synthase (psy) from daffodil and phyteon desatura (crtl) from bacteria. This ‘Golden Rice’ synthesize provitamin A (carotene) and can be solution for vitamin A deficiency particularly in under developed countries of Asia where Rice is the major food. Similarly, protein- rich potato variety is developed by transfering protein encoding genes from Amaranthus hypochondriaus.
This potato is a good source of carbohydrates as well as protein. Transgenic plants are developed to produce animal antibodies (known as plantibodies as developed by plant), interferon (protein that interfere with viral infection) and edible vaccines (e.g. hepatitis B antiviral protein gene transfered to banana to produce edible vaccine).
The first report of gene transfer and production of transgenic animal appeared in 1982 when a human growth hormone gene was transferred via microinjection to mouse. Because of the presence of a novel gene a huge increase in the body weight of mouse was seen. The basic purpose of production of transgenic animals has been to produce more protein in milk and meat, more meat, disease resistance, good quality wool etc.
Transgenic cattle (cow, sheep and goat) have been developed to contain therapeutic human proteins in their milk from where the protein is harvested. In 1991, Alan Colman and co-workers at Edinburgh produced five transgenic sheep, four female and one male. The milk of these transgenic sheep contained high amount of antitrypsin (antihemophilic factor). Transgenic pigs have been given human genes so that their organs carry human antigens. Their organs can be used for transplantation without being rejected by host.