Genetic engineering or Recombinant DNA technology or gene manipulation is a new-born discipline of science which is worked under highly controllable laboratory conditions to control the hereditary apparatus of a living cell i.e. the manipulation of genes under highly controllable laboratory condition , so that the cell can produce different chemicals or perform completely new functions. It is perhaps the finest output from the brains of biologists who have been interested in tailoring and manipulating heredity to the best man’s advantage. The onset of the new revolutionary technology of genetic engineering took place at Massachusetts Institute of technology.

Research on genetic engineering is centred in vitro joining of DNA fragments of different origins by the mediation of some highly specific enzymes to produce “recombinant – DNA” (gene splicing) which is then introduced into an appropriate host wherein it multiplies (gene clone).

In this way, immense possibilities are raised to bring about new gene combinations not occurring in nature. The science of recombinant- DNA technology or genetic engineering is still in its infancy but, even when it’s enormous potential impacts, both social and commercial, are clearly evident.

Genetic engineering takes the materials provide by nature, uses specialized knowledge and purpose to built tools to modify them in particular ways, and assembles the pieces to yield the final structure. Transferring genes from one organism to another is an alluring prospect since genetic engineering could reduce the cost and increase the supply industry and so on. Further more; there are many substances that occur naturally in only small quantities which might well prove invaluable if they were available in sufficient quantities genetic engineering.


Genetic engineering and agriculture:

So far inter-specific gene transfers were achieved through hybridization. These were restricted to sexually reproducing plant species. Inter specific gene transfers are now possible through recombinant DNA technology. Ti plasmids of Agro tumefacines and Ri plasmids of A-rhizogenes are being effectively used as vectors for gene transfer plants. By the end of 1992 more than 50 species of transgenic plants were produced many more have been produced which are resistant to insects, fungi, viruses and herbicides or which produce fruit with a longer shelf-life or have better taste or have higher yield.

Some of the successful gene transfers through Ti plasmid vectors are:

(a) Transfer of gene phasealin (G1 globin) from fresh bean or rajma to sunflower.


(b) Transfer of gene kenamycin resistance from E. Coli to tobacco and other plant species.

(c) Transfer of genes for leg-haemoglobin and RuBP – carboxylase from monocot wheat and maize to dicot plants.

(d) Transfer of genes for C4 photosynthetic pathway to C3 crop plants.

(e) Transfer of nitrogen fixation gene from the genome of bacterium Rhizobium in to chromosomes of non-leguminous plants. The work is also as to alter the genome of bacteria or of nonleguminous plants so that new symbiotic relationship can be developed and nonleguminous plants are also able to support these nitrogen-fixing bacteria.


(f) Transfer of frost-resistance genes to trees or crops so that these can be grown in snowy regions.

Production of Medicines:

Human genes for insulin, somato statin, thymosin, human growth hormone, and blood clotting factor VIII. C have been cloned to produce pure forms of those biologically important fine chemicals and hormones. In 1984, functional gonadotropic hormones were also obtained from transferred human cells.

Production of synthetic vaccines:


A large number of viral, bacterial and protozoan vaccines are being synthesized against pathogens causing hepatitis and liver cancer, rabies, foot and mouth disease of cattle (FMDC), feline leukemia causing cancer, cholera, malaria etc. Gene coding for an antigen protein is isolated from the pathogen and is cloned in a bacterial has or mouse cells, where it produces the concerned protein or the antigen. This is isolated and purified to be used as vaccines.

Example – Anti-hepatitis vaccine, Anti-rabbies vaccine, Antifoot and mouth disease vaccine for cattle, cholera vaccine and malaria vaccine.