The genome or the genetic material of an organism can be manipulated or, modified using different methodologies of biotechnology. Since the discovery of the double-helical structure of DNA in 1953 (Watson-Cricks-Wilkins-Franklin model), the genomes of innumerable organisms, from unicellular bacteria to multicellular human beings have been completely sequenced. It was understood that DNA is the universal component, and the same nucleotide building blocks are present in all organisms to store genetic information and make functional proteins. So, parts of DNA (Nucleotide sequences with 1 or more genes) can be identified, inserted, taken out, and/or inserted into other cells to make them capable to perform desired functions by genetically modifying them. In this article, we will have a deep insight into genetic engineering.
How it all started?
The basic understanding of the genetic modification processes began with the discovery of restriction enzymes and ligases, and the development of recombinant DNA molecule in the 1970s.
The discovery of the Polymerase chain reaction by Kary Mullis (in 1983) revolutionized the domain of biotechnology and genetics. Soon, Ti plasmids of Agrobacterium tumefaciens were first used as vector systems to insert useful genes in plants and by the mid-1990s genetically modified (GM) crops were being planted worldwide with altered genetic material to obtain better characteristics like resistance to pests, diseases etc. In 1997, scientists created Dolly (the first cloned sheep) using adult sheep cells.
How is it done?
The basic steps of genetic engineering can be listed as follows –
- The identification and extraction of desired DNA fragments.
- The insertion of these fragments to a vector genome, e.g., bacterial plasmids, and the formation of recombinant DNA.
- The introduction and growth of recombinant vector in recipient host organisms.
Applications of genetic engineering
The applications are innumerable, but we can divide them into the following categories broadly –
Plant breeding used to be completely phenotype-based, without any knowledge of their genetic composition. Crops were grown, selected (based on their phenotypes) and harvested, which required a lot of time and resources. With the application of molecular biology in plant breeding in the 1980s, the genetic components of phenotypes like, DNA based molecular markers were studied and identified. The marker-assisted selection (MAS) helped in the easier and quick selection of desired forms of genes for individual plants.
Gradually, with the advent of recombinant DNA technology, the genetic constituents of crops were modified to increase their production, nutritional quality and quantity, increased post-harvest shelf life, and resistance to temperature, humidity, pests and diseases. Some crops have been genetically modified (transfer of nitrogen-fixing genes from leguminous plants to cereal crops) so that they don´t depend on fertilizers as they can directly fix atmospheric nitrogen.
Genetic engineering has been used to produce a variety of medicines, vaccines, enzymes and hormones. Recombinant DNA vaccines are produced with the outside coat protein of the microorganism which is a much safer delivery of antigen than the conventional vaccines. Recombinant DNA vaccines for hepatitis B virus, and malaria is undergoing trials for future use.
Similarly, hormones produced by genetically modified organisms are safer and cheaper because of fewer chances of contamination during their mass production, e.g., commercially available insulin and human growth hormone from recombinant E. coli has become cheaper than earlier.
Moreover, genome mapping has paved the way to study the inheritance of genetic diseases and the genes responsible for them. A complete genome map of healthy individuals and their parents can predict and prevent a lot of diseases that are being studied to have a genetic predisposition.
The most revolutionary step has been the invention of ‘gene therapy’ where healthy genes are introduced directly to a person with malfunctioning/problematic genes. Successful clinical trials have been approved for a lot of diseases like AIDS, high cholesterol, cancer, cystic fibres emphysema, muscular dystrophy, adenosine deaminase deficiency, etc.
Recombinant DNA technology and its applications have huge scope and future in an alternative source of energy production. Biofuels or genetically modified bioengineered energy crops are the need of the hour, which can be processed into alcohols, diesel, oils etc. Research is being conducted to transfer genes responsible for the conversion of garbage and industrial wastes into sugar and alcohol.
Also, genetically modified organisms are being exploited to clean up environmental contaminants, for example, oil spills can be cleared by new strains of pseudomonads and some yeasts. Recombinant microorganisms are also used to develop biological pesticides which would diminish the soil pollution caused by the overuse of chemical insecticides.
Recombinant DNA technology has multiple applications in a variety of industries. Genetically modified microbes can be used to synthesize organic chemicals at a large scale, for example, microbes have been developed for the conversion of cellulose to sugar and then, ethanol.
The introduction of desired genes in animals to improve the quality and quantity of meat, milk and other animal products have been very helpful for better livestock production and in turn, has immensely contributed to the growth of associated food industries.
Ethical, moral and other challenges
Since its early days, gene manipulation or genetic engineering has invited controversies and potential threats to the ethical and religious belief systems of human society. Genetically modified food is still not universally accepted by human society as a large group of people have ethical concerns about their consumption and even, have doubts regarding their possible allergic reactions or, some side effects. Moreover, the interaction of genetically engineered organisms with other organisms in a natural environment is still unpredictable and has not been completely studied and understood yet.
The ability to manipulate genes might pave the ways for biological weapons. Also, the possibility of the creation of human clones or genetically engineered babies with selective genetic traits like eye colour, skin colour, or even gender, would lead to genetic supremacy or create alarming disparity in society.
- P. J. Greenaway (1980) Basic steps in genetic engineering, International Journal of Environmental Studies, 15:1, 11-24, DOI: 10.1080/00207238008737419 http://dx.doi.org/10.1080/00207238008737419
- Muntaha et al (2016) Applications and future prospects of genetic engineering: a new global perspective, FUUAST Journal of Biology, 6(2): 201-209.