Biotechnology and Its Applications: Notes and PYQs

Biotechnology is the use of living organisms, cells or their parts, together with enzymes, to make products and processes useful to human beings. Brewing, baking and curd setting are its old forms; the modern subject began in the nineteen seventies, when scientists learnt to cut a gene out of one organism and join it to the DNA of another. That technique, called recombinant DNA technology or genetic engineering, has given insulin made by bacteria, crops that resist insects, vaccines without the whole virus and a test that can identify a person from a trace of tissue. Examiners ask this chapter for its tools, its named products and the bodies that regulate it.

The tools of recombinant DNA technology

The steps of the work are the same whatever the product: isolate the DNA, cut it with a restriction enzyme, join the gene to a vector, put the construct into a host, select the cells that took it, grow them in a bioreactor and purify the product in what is called downstream processing.

Applications in agriculture

• Bt cotton carries cry genes taken from the soil bacterium Bacillus thuringiensis, whose protein becomes toxic in the alkaline gut of the bollworm and kills it, while remaining an inactive crystal in the plant.
• Golden Rice was engineered to make beta carotene, the precursor of vitamin A, to reduce blindness caused by its deficiency.
• Pest resistance has also been produced by RNA interference, which silences a gene of the nematode that attacks tobacco roots.
• Tissue culture allows thousands of identical plants, called somaclones, to be raised from a small explant, because a plant cell is totipotent; this micropropagation is used for banana, sugarcane and orchids, and meristem culture gives virus free planting material.
• Somatic hybridisation fuses protoplasts of two plants, the pomato from potato and tomato being the classic laboratory example.
• Biofertilisers such as Rhizobium, Azotobacter, blue green algae and mycorrhiza, and biopesticides such as Bacillus thuringiensis and the fungus Trichoderma, reduce the need for chemicals.

Applications in medicine

Human insulin was the first medicine of this kind. Insulin is made in the body as proinsulin with an extra C peptide; in 1983 the American company Eli Lilly put the sequences of the A and B chains into Escherichia coli, produced them separately and joined them to make the first recombinant human insulin, sold as Humulin. Gene therapy, the replacement of a defective gene, was first attempted in 1990 on a girl who lacked the enzyme adenosine deaminase. Molecular diagnosis uses the polymerase chain reaction to find a pathogen before symptoms appear and the ELISA test to detect antigens or antibodies, as in the testing for the human immunodeficiency virus. Recombinant vaccines, such as the one for hepatitis B, use a single protein of the virus instead of the whole organism, so they cannot cause the disease. Transgenic animals are reared to carry human genes, and Dolly the sheep, produced at the Roslin Institute in Scotland in 1996 by transferring the nucleus of a body cell into an egg, was the first mammal cloned from an adult somatic cell. Gene editing with the CRISPR and Cas9 system, for which the Nobel Prize in Chemistry was awarded in 2020 to Emmanuelle Charpentier and Jennifer Doudna, now allows a sequence to be changed in place.

Identification, patents and regulation

DNA fingerprinting, developed by Alec Jeffreys in 1984, compares repeated sequences that differ from person to person and is used in criminal investigation, in disputed parentage and in identifying victims of a disaster; the Centre for DNA Fingerprinting and Diagnostics at Hyderabad does this work in India. The patenting of knowledge that a community has long used is called biopiracy, and India fought such claims over turmeric, neem and basmati rice. In India biotechnology is promoted by the Department of Biotechnology, set up in 1986, and the release of a genetically modified organism is cleared by the Genetic Engineering Appraisal Committee under the Ministry of Environment, Forest and Climate Change, while the Human Genome Project, completed in the first years of this century, provided the map on which much of this work now rests.