NCERT Exemplar: Biotechnology & its Applications - 2 | Biology Class 12 - NEET PDF Download

SHORT ANSWER TYPE QUESTIONS

Q.1. Gene expression can be controlled with the help of RNA. Explain the method with an example.
Ans. Gene expression can be controlled by using RNA molecule. The technology is called RNA interference or RNAi. It is used to block the expression of certain genes and also referred to as gene silencing. During this process a complementary RNA to the mRN A being produced by the gene is introduced into the cell. This RNA binds to the mRNA making it double stranded and therefore stops translation. Resistance to nematode Meloidogyne incognita in tomato has been achieved by this method.

Q.2. Ignoring our traditional knowledge can we prove costly in the area of biological patenting. Justify.
Ans. Most of the industrialised nations are rich financially but poor in biodiversity and traditional knowledge. In contrast the developing and the underdeveloped world is rich in biodiversity and traditional knowledge related to bio-resources. Traditional knowledge related to bio-resources can be exploited to develop modem applications and can also be used to save time, effort and expenditure during their commercialisation. There has been” growing realisation of the injustice, inadequate compensation and benefit sharing between developed and developing countries. Therefore, some nations are developing laws to prevent such unauthorised exploitation of their bio-resources and traditional knowledge.

Q.3. Highlight any four areas where genetic modification of plants has been useful.
Ans. Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has
(i) Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
(ii) Reduced reliance on chemical pesticides (pest-resistant crops).
(iii) Helped to reduce post-harvest losses.
(iv) Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).

Q.4. What is a recombinant DNA vaccine? Give two examples.
Ans. A recombinant vaccine is a vaccine produced through recombinant DNA technology. This involves inserting the DNA encoding an antigen that stimulates an immune response into bacterial or mammalian cells. Recombinant DNA technology has allowed the production of antigenic polypeptides of pathogen in bacteria or yeast. Vaccines produced using this .approach allow large scale production and hence greater availability for immunisation, e.g., hepatitis B vaccine (Recombivax HB) produced from yeast. As of June 2015 one human DNA vaccine had been approved for human use, the single-dose Japanese encephalitis vaccine called IMOJEV, released in 2010 in Australia.

Q.5. Why is it that the line of treatment for a genetic disease is different from infectious diseases?
Ans. If a person is born with a hereditary disease, can a corrective therapy be taken for such a disease? Gene therapy is an attempt to do this. Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo.

Q.6. Discuss briefly how a probe is used in molecular diagnostics.
Ans. A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarily with the mutated gene.

Q.7. Who was the first patient who was given gene therapy? Why was the given treatment recurrent in nature?
Ans. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by – enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem- with both of these approaches that they are not completely curative. As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires “periodic infusion of such genetically engineered lymphocytes. However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

Q.8. Taking examples under each category, discuss upstream and downstream processing.
Ans. Upstream processing: Biotechnological processes can be separated into upstream processes and downstream processes. The upstream process is defined as the entire process from DNA isolation and culture expansion of the cells until final product.
Downstream processing: After completion of the biosynthetic stage, the product has to be subjected through a series of processes before it Is ready for marketing as a finished product. The processes include separation and purification, which are collectively referred to as downstream processing. The product has to be formulated with suitable preservatives. Such formulation has to undergo through clinical trials as in case of drugs. Strict quality control testing for each product is also required. The downstream processing and quality control testing vary from product to product.

Q.9. Define Antigen and Antibody. Name any two diagnostic kits based upon them.
Ans. An antigen is a foreign substance that elicits the formation of an antibody. Antibody is a protein that is synthesised in response to an antigen. Antigen and antibody show high degree of specificity in binding each other. Two diagnostic kits based on antigen-antibody interaction are:
(a) ELISA for HIV.
(b) Pregnancy test kits.

Q.10. ELISA technique is based on the principles of antigen-antibody interaction. Can this technique be used in the molecular diagnosis of a genetic disorder, such as phenyketonuria?
Ans. Yes. One can use antibody against the enzyme (that is responsible for the metabolism of phenylalanine) to develop ELISA based diagnostic technique. The patient where the enzyme protein is absent would give negative result in ELISA when compared to normal individual.

Q.11. How is a mature, functional insulin hormone different from its prohormone form?
Ans. Mature functional insulin is obtained by processing of pro-hormone which contains extra peptide called C-peptide. This C-peptide is removed during maturation of pro-insulin to insulin.

Q.12. Gene therapy is an attempt to correct a genetic defect by providing a normal gene into the individual. By this the normal function can be restored. An alternate method would be to provide the gene product (protein/enzyme) known as enzyme replacement therapy, which would also restore the function. Which in your opinion is a better option? Give reason for your answer.
Ans. Enzyme replacement therapy works on artificially administering the required enzyme into the patient’s body. This helps in management of the disease. But this needs frequent re-administration of enzyme and other necessary drugs to continue the therapy. In most of the cases; the therapy is costly and is a cause of financial and emotional drain on the patient. Using gene correction is a permanent solution. For example; a person with ADA deficiency can be permanently cured if the required gene is introduced during the embryo stage. This will ensure a better quality of life for the patient.

Q.13. Transgenic animals are the animals in which a foreign gene is expressed. Such animals can be used to study the fundamental biological process, phenomenon as well as for producing products useful for mankind. Give one example for each type.
Ans. Study of basic biological process—how genes are regulated, how they affect the normal functions of the body and its development. Transgenic cow, Rosie is an example for the second category.

Q.14. When a foreign DNA is introduced into an organism, how is it maintained in the host and how is it transferred to the progeny of the organism?
Ans. Foreign gene is usually ligated to a plasmid vector and introduced in the host. As plasmid replicates, and makes multiple copies of itself, so does the foreign gene gets replicated and its copes are made. When the host organism divides, its progeny also receives the plasmid DNA containing the foreign gene.

Q.15. Bt cotton is resistant to pest, such as lepidopteron, dipterans and coleopterans. Is Bt cotton also resistant to other pests as well?
Ans. Bt cotton is made resistant to only certain specific taxa of pests. It is quite likely that in future, some other pests may infest this Bt cotton plants. It has similar immunisation against small-pox which does not provide immunity against other pathogens like those that cause cholera, typhoid etc.

LONG ANSWER QUESTIONS 

Q.1. A patient is suffering from ADA deficiency. Can he be cured? How?
Ans. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches that they are not completely curative. As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

Q.2. Define transgenic animals. Explain in detail any four areas where they can be utilised.
Ans. Transgenic animals are the products of genetic engineering and express specific gene(s) from totally unrelated source. Following are the four main areas where they can be utilised:
(1) To study normal physiology and development these animals can be used to study as to which factor/gene products are needed at what time of development. By expression of certain genes, they help scientists to understand the normal gene expression at various stages of growth and development.
(2) Study of Diseases: Transgenic animals can be created to serve as models for various human diseases. They also help us understand the involvement of various genes in diseases like cancer, Parkinson’s disease etc.
(3) Vaccine safety: Transgenic animals can be used to test vaccines like polio vaccine. Transgenic mice have shown promising results in this area and would replace the vaccine testing on monkeys in the years to come.
(4) Chemical safety testing: Transgenic animals are created which are more sensitive to certain chemicals/drugs. These are used to study the toxicity or side effects of that chemical/drug. The advantage is that we get results faster.

Q.3. You have identified a useful gene in bacteria. Make a flow chart of the steps that you would follow to transfer this gene to a plant.
Ans. After identifying a useful gene in bacteria, following steps should be undertaken:
(1) Isolation of useful gene using.
Restriction Endonucleases
                             ↓
(2) Transferring the gene to a suitable vector to create a recombinant DNA molecule
                             ↓
(3) Transfer of these recombinant DNA molecules to the target cells
                             ↓
(4) Screening of cells for transformation
                             ↓
(5) Selection of transformed cells
                             ↓
(6) Regeneration of plants from the transformed cells to get transgenic plants.

Q.4. Highlight five areas where biotechnology has influenced our lives.
Ans. The applications of biotechnology include:

1. therapeutics and diagnostics
2. genetically modified crops for agriculture
3. processed food
4. bioremediation
5. waste treatment and energy production.

Q.5. What are the various advantages of using genetically modified plants to increase the overall yield of the crop?
Ans. GM plants have been useful in many ways. Genetic modification has:

1. Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
2. Reduced reliance on chemical pesticides (pest-resistant crops).
3. Helped to reduce post-harvest losses.
4. Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
5. Enhanced nutritional value of food.
   Example:  Vitamin ‘A’ enriched rice.

In addition to these uses, GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals.

Q.6. Explain with the help of one example how genetically modified plants can:
(a) Reduce usage of chemical pesticides
(b) Enhance nutritional value of food crops
Ans. 
(a) Reduce usage of chemical pesticides: Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt for short). Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides; in effect created a bio-pesticide. Examples are Bt cotton, Bt com, rice, tomato, potato and soyabean etc.
(b) Enhance nutritional value of food crops: Golden rice is the transgenic variety of basmati rice which gives high yield and rich in vitamin A, so it is used in the deficiency of vitamin-A causing night blindness and skin disorder.

Q.7. List the disadvantages of insulin obtained from the pancreas of slaughtered cows and pigs:
Ans. 

1. Insulin being a hormone is produced in very little amounts in the body.
   Hence, a large number of animals need to be sacrificed for obtaining small quantities of insulin. This makes the cost of insulin very high. [Demand being many fold higher than supply].
2. Slaughtering of animals is also not ethical.
3. There is potential of immune response in humans against the administered insulin which is derived from animals.
4.  There is possibility of slaughtered animals being infested with some infectious micro organism which may contaminate insulin.

Q.8. List the advantages of recombinant insulin.
Ans. Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin. The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form. In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.

Q.9. What is meant by the term bio-pesticide? Name and explain the mode of action of a popular bio-pesticide.
Ans. Biopesticide is a pesticide which is
(a) not chemical in nature
(b) more specific in action against the pest
(c) safer for environment than chemical pesticides
A popularly known bio-pesticide is Bt toxin, which is produced by a bacterium called Bacillus thuringiensis. Bt toxin gene has been cloned from this bacterium and expressed in plants. Bt toxin protein when ingested by the insect, gets converted to its active form due to the alkaline pH of the gut. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually kills the insect.

Q.10. Name the five key tools for accomplishing the tasks of recombinant DNA technology. Also mention the functions of each tool.
Ans. 

1. Restriction endonucleases: for cutting the desired DNA at desired places
2. Gel electrophoresis: for separating the desired DNA fragments
3. Ligase enzyme: for creating recombinant DNA molecule.
4. DNA delivery system: like electroporation, microinjection, gene gun method.
5. Competent host (usually bacteria/yeast): to take up recombinant DNA.