Biotechnology and its Applications: common doubts, answered
The questions students ask most often about Biotechnology and its Applications, each with a short answer. For the full chapter, read the Biotechnology and its Applications notes.
About the chapter
How many recombinant therapeutics are there and what advantages do they have over earlier ones?
About 30 recombinant therapeutics have been approved for human use worldwide, and 12 of these are marketed in India. Producing them in bacteria or other hosts avoids the immune reactions caused by animal-derived products, and also avoids contamination with pathogens, so they are safer. Human insulin is the standard example.
Three research areas
Read this section in the notes →What are the three critical research areas of biotechnology?
These are an effective catalyst, which may be an improved organism or a purified enzyme; engineering the right conditions for that catalyst to work; and downstream processing to purify the final protein or organic compound. Together they cover the path from the living agent to a usable product.
Food production and tissue culture
Read this section in the notes →What is totipotency and how is it used in micro-propagation?
Totipotency is the capacity of any plant cell or explant to grow into a whole plant. In micro-propagation, tiny pieces of tissue are grown on a nutrient medium with sucrose, salts, vitamins, amino acids, auxins and cytokinins, and thousands of plants can be produced. The plants are genetically identical to the parent and are called somaclones.
Meristem culture and somatic hybrids
Read this section in the notes →Why is meristem culture used to get virus-free plants?
Even in a virus-infected plant, the apical and axillary meristems are free of virus. A piece of meristem can therefore be removed and grown in vitro to give a healthy plant. This is used for crops like banana, sugarcane and potato. Taking the whole infected plant would not remove the virus.
What is a somatic hybrid and what is a pomato?
A somatic hybrid is formed by fusing protoplasts, which are cells with the wall removed, from two different plants and growing the fused cell into a plant. The pomato is the hybrid of tomato and potato. It was not commercially useful because it did not have all the desired characters of the two crops.
Genetically modified crops
Read this section in the notes →What are the benefits of genetically modified crops?
GM crops can be made more tolerant to abiotic stresses such as cold and drought, resistant to pathogens and pests, and they reduce the reliance on chemical pesticides. They can reduce post-harvest losses and improve nutritional value, and they raise the efficiency of mineral use. Golden rice, enriched with vitamin A, is a good example.
Bt cotton
Read this section in the notes →How does Bt toxin kill an insect without harming the bacterium that makes it?
The Bacillus thuringiensis bacterium produces the toxin as an inactive protoxin crystal, so it does not harm itself. In the alkaline gut of the insect, the crystals dissolve and the toxin gets activated. It then makes pores in the midgut epithelial cells, causing the cells to swell and burst, and the insect dies.
Which Bt toxin gene controls which pest?
The cryIAc and cryIIAb genes encode proteins that control cotton bollworms, while cryIAb controls the corn borer. The different Bt proteins are specific to groups such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). Pairing the gene with the right pest is a favourite question.
RNA interference
Read this section in the notes →How does RNA interference protect tobacco plants from a nematode?
The nematode Meloidogyne incognita infects tobacco roots and lowers yield. Agrobacterium was used to introduce into the plant DNA that makes both sense and anti-sense RNA. These form a double-stranded RNA that silences the nematode's specific mRNA, so the parasite cannot survive in the transgenic host. No toxin protein is involved.
What is RNAi and how does it work in general?
RNAi is a cellular defence found in all eukaryotes in which a double-stranded RNA silences a particular gene. One strand is complementary to that gene's mRNA, binds to it and prevents its translation. The double-stranded RNA can come from viruses with RNA genomes or from transposons that copy themselves through an RNA intermediate. Biotechnologists exploit it to silence chosen genes in pests.
Genetically engineered insulin
Read this section in the notes →What is the difference between pro-insulin and mature insulin?
Mature insulin has two short polypeptide chains, A and B, held together by disulphide bridges. In humans it is made as pro-insulin, which has an extra C peptide that is removed during maturation. So the mature hormone lacks the C peptide, which is why pro-insulin is not the final hormone.
How was insulin produced using E. coli?
Eli Lilly prepared two DNA sequences, corresponding to chain A and chain B of human insulin, and introduced them into plasmids of E. coli to produce the chains separately. The chains were then extracted and combined by making disulphide bonds, giving human insulin. The C peptide was not needed in this approach.
Gene therapy
Read this section in the notes →What is gene therapy and what was its first clinical case?
Gene therapy is a set of methods to correct a gene defect diagnosed in a child or an embryo, by delivering normal genes to compensate for the non-functional ones. The first clinical gene therapy was given in a 4-year-old girl with adenosine deaminase (ADA) deficiency, who was treated with her own lymphocytes carrying a functional ADA cDNA.
Why is ADA gene therapy with lymphocytes not a permanent cure?
The lymphocytes taken from the patient and given the functional ADA gene are not immortal, so the patient needs periodic infusions of such cells. A permanent cure would need the gene to be introduced into cells at early embryonic stages, so that it works throughout life.
Molecular diagnosis
Read this section in the notes →How does molecular diagnosis differ from conventional diagnostic methods?
Conventional tests, such as serum or urine analysis, work only when the pathogen has reached a high concentration or symptoms have appeared. PCR can detect low concentrations of bacteria or viruses, even before symptoms, so it is used for early detection of HIV. ELISA detects antigens or antibodies through their interaction.
What is the principle of ELISA?
ELISA is based on the principle of antigen-antibody interaction. The presence of a pathogen is detected either by the antigens it makes or by the antibodies produced against it in the person's body. A positive reaction gives a visible signal. It is used, for instance, in the preliminary screening for HIV infection.
Transgenic animals
Read this section in the notes →What are transgenic animals and why are they made?
Transgenic animals are those whose DNA has been manipulated to possess and express a foreign gene. More than 95 per cent are mice. They are made to study how genes regulate normal physiology, to model human diseases, to produce biological products such as α-1-antitrypsin for emphysema, for vaccine safety testing such as polio, and for chemical safety testing.
What was special about Rosie the transgenic cow?
Rosie was the first transgenic cow, and her milk contained the human protein alpha-lactalbumin at 2.4 grams per litre. The milk was thus nutritionally more balanced for human babies than the natural cow's milk, being a richer source of protein. The gene was introduced into the cow.
Ethical issues and biopiracy
Read this section in the notes →What is biopiracy?
Biopiracy is the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned, and without compensatory payment. A patent granted in the US on Basmati rice, developed from Indian farmers' varieties, is a well-known case that caused concern in India.
What is the role of GEAC?
The Genetic Engineering Approval Committee is the body set up by the Indian government to decide the validity of GM research and the safety of introducing GM organisms for public services. The full form is a common error: it is Approval, not Advisory, in GEAC.
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