Biotechnology and its Application Class 12 Biology Important Questions

Please refer to Biotechnology and its Application Class 12 Biology Important Questions with solutions provided below. These questions and answers have been provided for Class 12 Biology based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these problem solutions as it will help them to gain more marks in examinations. We have provided Important Questions for Class 12 Biology for all chapters in your book. These Board exam questions have been designed by expert teachers of Standard 12.

Class 12 Biology Important Questions Biotechnology and its Application

Diagram Type Questions

Question. Which of the following is the correct set of the labels A, B, C and D in the given figure of maturation of pro-insulin into insulin ?

A	B	C	D
(a) Proinsulin	cell peptidases	Insulin	Free C-Peptide
(b) Insulin	cell peptidases	Free C-Peptide	Proinsulin
(c) Insulin	Free C-Peptide	cell peptidases	Proinsulin
(d) Insulin	Proinsulin	Free C-Peptide	cell peptidases

Critical Thinking Type Questions

Question. Transgenic animals has been successfully used for producing
(a) transgenic mice for testing safety of polio vaccine before use in humans.
(b) transgenic models for studying new treatments for certain cardiac diseases.
(c) transgenic cow – rosie which produces high fat milk for making ghee.
(d) animals like bulls for farm work as they have super power.

Question. Which one of the following techniques made it possible to genetically engineer living organism ?
(a) Recombinant DNA techniques
(b) X-ray diffraction
(c) Heavier isotope labelling
(d) Hybridization

Question. A transgenic food crop which may help in solving the problem of night blindness in developing countries is
(a) golden rice
(b) Bt soyabean
(c) flavr – savr tomato
(d) starlink maize

Question. The genetic defect, adenosine deaminase (ADA) deficiency may be cured permanently by
(a) administering adenosine deaminase through injection
(b) bone marrow transplantation
(c) enzyme replacement therapy
(d) introducing isolated gene from marrow cells producing ADA into the cells at early embryonic stages

Question. Main objective of production/use of herbicide resistant GM crops is to
(a) eliminate weeds from the field without the use of manual labour.
(b) eliminate weeds from the field without the use of herbicides.
(c) encourage eco-friendly herbicides.
(d) reduce herbicide accumulation in food articles for health safety.

Question. Cry II Ab and cry I AC produce toxins that control
(a) cotton bollworms and corn borer respectively.
(b) cotton borer and cotton bollworms respectively.
(c) tobacco budworms and nematodes respectively.
(d) nematodes and tobacco budworms respectively.

Question. RNA interference involves
(a) synthesis of mRNA from DNA.
(b) synthesis of cDNA from RNA using reverse transcriptase.
(c) silencing of specific mRNA due tocomplementary RNA.
(d) interference of RNA in synthesis of DNA.

Question. What is the disadvantage of using porcine insulin (from pig) in diabetic patients?
(a) It leads hypercalcemia.
(b) It is expensive.
(c) It may cause allergic reactions.
(d) It can lead to mutation in human genome.

Question. In order for gene therapy to be most effective, genes should be inserted in
(a) WBC
(b) RBC
(c) stem cells
(d) all of these

Question. Deliberate alteration of genome for treatment of disease is called
(a) transformation rescue
(b) imprinting
(c) exon shuffle
(d) gene therapy

Very Short Answer Questions

Question. Why are mango trees unable to grow in temperate climate?
Answer : Because temperature affects the basal metabolism/ physiological function of the plant not adapted to low temperature of temperate climate. Mango trees are not able to grow in temperate below 30 degrees thus cannot grow in temperate climate.

Question. Name one of the ex-situ conservation method for endangered species
Answer : Cryopreservation is one of the ex-situ conservation methods for endangered species.

Question. Write the level of biodiversity represented by mangrove. Give another example falling in the same level.
Answer : Mangroves represent ecological diversity. The same level of biodiversity is also shown by rain forests, coral reefs wetlands, estuaries and alpine meadows,
etc.

Question. Write the function of ‘‘Sacred groves’’.
Answer : Sacred groves are a method for In situ conservation of biodiversity and conserving rare threatened species.

Question. Why Western Ghats in India have been declared as biological hotspots ?
Answer : Due to greater species diversity/presence of endemic species.

Question. How the species-area relationship is represented on a log scale ?
Answer : The species-area relationship is represented in linear form on a log scale.

Question. Suggest a molecular diagnostic procedure that detects HIV in suspected AIDS patients.
Answer : PCR and ELISA

Question. Write the use of stem cells. 
Answer : Stem cells can be used to grow new cells in a laboratory to replace damaged organs or tissues.  

Question. What are Cry genes ? In which organism are they present ? 
Answer : The genes which code for Bt toxin / Cry proteins (toxic proteins), Bacillus thuringiensis.

Question. List the type of cry genes that provide resistance to corn plants and cotton plants respectively against lepidopterAnswer :
Answer : cryIAc / cryIIAb – cotton.

Question. Bt-toxins are released as inactive crystals in the bacterial body. What happens to it in the cotton bollworm body that it kills the bollworm.
Answer : It is converted into an active protein (due toalkali ne pH of the gut of the bollworm). The toxin binds to midgut cells / create pores / causes cell swelling and lysis that kills the bollworm.

Question. What are stem cells ? 
Answer : Stem cells are undifferentiated or “blank” cells. This means they are capable of developing into cells that serve numerous functions in different parts of the body. 

Question. Name the specific type of gene that is incorporated in a cotton plant to protect the plant against cotton bollworm infestation.
Answer : Bt toxin genes.

Question. Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin.
Answer : Removal of C-peptide (from pro-insulin).

Question. What is biopiracy ?
Answer : Illegal / non authorized / non compensated use of bioresources by organisations.

Question. What are transgenic animals. Give an example.
Answer : Animals whose DNA is manipulated to possess and express an extra (foreign) gene e.g., Rosie -transgenic cow.

Question. State the cause of adenosine deaminase enzyme deficiency. 
Ans. Deletion of gene for adenosine deaminase.

Question. What is “Flavr Savr”?
Ans. It is a transgenic tomato variety which has blocked production of polygalacturonase.

Question. Suggest any two possible treatments that can be given to a patient exhibiting adenosine deaminase deficiency.
Ans. (i) Enzymes replacement therapy (in which functional ADA is injected)
(ii) Bone marrow transplantation
(iii) Gene therapy/Culturing the lymphocytes followed by introduction of functional ADA
cDNA into it and returning it into the patient’s body. (Any two)

Question. Why do children cured by enzyme-replacement therapy for adenosine deaminase deficiency need periodic treatment? 
Ans. As enzyme replacement therapy does not cure the disease completely, it requires periodic treatment.

Question. What are Cry proteins? Name an organism that produce it. How has man exploited this protein to his benefit?
Ans. Cry protein (crystal protein) is a toxin coded by a gene cry and is poisonous to some insects, thus giving resistant characters to the plants. Bacillus thuringiensis produces Cry protein. Cry protein producing gene is transferred to the plants to provide resistance against insect larvae. Man has developed several transgenic crops by introducing these genes from bacteria to crop plants such as Bt cotton, Bt corn, etc.

Question. What are transgenic animals? Give an example. 
Ans. Animals that have had their DNA manipulated, to possess and express an extra (foreign) gene are known as transgenic animals. Example, Rosie is a transgenic cow.

Question. What is biopiracy? 
Ans. Biopiracy is the use of bioresources by multinational companies and other organisations without proper authorization or compensation payment to the concerned country or organisation.

Question. State the purpose for which the Indian Government has set up GEAC.
OR
Mention two objectives of setting up GEAC by our government. 
Ans. GEAC was set up to make decisions regarding the validity of GM research and the safety of introducing GM-organisms for public services.

Question. What are transgenic bacteria? Illustrate using any one example.
Ans. The bacteria whose DNA is manipulated to carry and express a foreign DNA is called transgenic bacteria. These microbes are used for producing important biochemicals. They have been synthesising alcohol, enzymes, steroids and antibiotics. Example, Bacillus thuringiensis for Bt cotton. For details refer basic concept point 1(i) and 2(i).

Short Answer Questions

Question. Explain how Eli Lilly an American companypro duced insulin by recombinant DNA technology. U [Delhi/Outside Delhi, Comptt.
OR
Explain how the company Eli Lilly was able to produce human insulin using rDNA technique.
OR
Recombinant DNA-technology is of great importance in the field of medicine. With the help of a flow chart, show how this technology has been used in preparing genetically engineered human insulins.
Answer : In 1983, Eli Lily and American company prepared two DNA sequences corresponding to A and B chains of human insulin, 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.

Question. (a) What are transgenic animals ?
(b) Name the transgenic animal having the largest number amongst all the existing transgenic animals.
(c) Mention any three purposes for which these animals are produced.
Answer : (a) Animals that have had their DNA manipulated to possess and express an extra / foreign gene. 
(b) Mice. ½
(c) (i) Normal physiology and development.
(ii) Study of disease.
(iii) Biological products.
(iv) Vaccine safety.
(v) Chemical safety testing. (Any three)

Question. Explain the events that occur in the host cell on introduction of nematode-resistant gene into the tobacco plant by using Agrobacterium vectors.
Answer : l RNA interference ½
l Silencing of a specific mRNA due to a complementary RNA ½
l dsRNA/Introduction of DNA was such that it produced both sense/ and anti-sense RNA in the host cells/these two RNAs formed dsRNA that initiated RNAi.

Question. What are the objectives of GEAC ?
OR
Mention two objectives of setting up GEAC by our government.

Answer : Objectives of GEAC :
(i) To examine the validity of GMO i.e., genetic modification of organisms research.
(ii) Safety of introducing GMOs for public use. 

Question. State the initiative taken by the Indian Parliament towards biopiracy ? 
Answer : Indian Parliament has passed the second amendment of the Patent Bill, which deals with patent terms, emergency provisions and research and development initiatives.

Question. Explain the role of Agrobacterium tumefaciens in developing resistance in tobacco plant against nematode Meloidegyne incognitia.
Name the processes responsible for this.
Answer : Agrobacterium tumefaciens is capable of transforming a piece of their own genome termed as T-DNA into the infected plant cells to create the desired GMO.
A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. RNA interference (RNAi) strategy is used to prevent this infestation.
RNAi is a method of cellular defence in all eukaryotic organisms. It is a process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of mRNA. It prevents the translation of a specific mRNA (silencing) due to a complementary dsRNA molecule. Using Agrobacterium vectors, nematodespecific genes (DNA) were introduced into the
host plant (Tobacco plant). The introduction of DNA produces both sense and anti-sense RNA in the host cells. These two RNA molecules being complementary to each other form a double stranded RNA (dsRNA) that initiates RNAi and thus, silences the specific mRNA of nematode. The consequence was that the parasite cannot survive in a transgenic host expressing specific interfering RNA.

Question. (a) Mention the cause of ADA deficiency in humAnswer :
(b) How is gene therapy carried out to treat the patients suffering from this disease?
(c) State the probability of a permanent cure of this disease.
Answer : (a) The disease is caused by a mutation in a gene on chromosome 20. The gene codes for the enzyme ADA. It is an inherited disorder that damages the immune system.
(b) ADA is very crucial for the immune system to function. The deficiency of ADA causes severe combined immunodeficiency disease. The patient lacks functional T-lymphocytes and
fails to fight the infectious pathogens.
Using gene therapy, lymphocytes are extracted from the patient’s bone marrow and a normal functional gene for ADA is introduced into these lymphocytes with the help of the retrovirus.
The lymphocytes of bone marrow contain the functional ADA gene and reactivate the patient’s immune system.
(c) 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 is that they are not completely cured. If the gene isolated from bone marrow cells producing ADA is
introduced into cells at early embryonic stages, it could be a permanent cure.

Question. What are some applications and advantages of stem cell technology ? 
Answer : Applications of stem cells technology : Stem cells are special human cells which are able to develops into many different cell types. This can range from muscle cells to brain cells. In some cases they can also fix damage tissues. Stem cells are divided into two main forms. They are embryonic stem cells and adult stem cells. They are used in treating several
clinical problems like :
(i) Tissue regeneration.
(ii) Damaged myocardium after heart infraction.
(iii) Brain after stroke.
(iv) Spinal cord after mechanical injury.
Advantages of stem cells :
(i) Adult stem cells have low rejection can rate. 
(ii) Stem cells, having regenerative property can be used in replacing any organ, which is not working or failing.
(iii) They can help in studying human growth and cell development.
(iv) They can be used to test the effects of medicinal drugs and medicine without the use of animals.

Question. Specific Bt toxin genes isolated from Bacillus thuringiensis incorporated into cotton is coded by the genes cryIAc and cryIIAb that control the cotton bollworms. Mention its mode of action.
Answer : (i) Bacillus forms protein crystals that contain a toxic insecticidal protein.
(ii) Once an insect ingests the inactive toxin, it is converted into an active form.
(ii) The toxin in the form of crystals gets solubilised due to alkaline pH in the gut.
(iv) The activated toxin binds to the surface of gut epithelial cells and perforate the walls causing
the death of insect larva.

Question. What is GMO ? List any five possible advantages of a GMO to a farmer OR
People are quite apprehensive to use GM crops. Give three arguments in support of GM crops so as to convince the people in favour of such crops.
Answer : Plants / bacteria / fungi / animals whose genes have been altered by manipulation. 
Tolerance to abiotic stresses / like cold / drought /salt / heat, reduced reliance on chemical pesticides /pest resistant crops, reduce post-harvest losses,increased efficiency of mineral usage by plants, enhanced nutritional value to create tailor-made plant.

Question. Differentiate between gene therapy and gene cloning.
Ans. Table 12.1: Difference between Gene Therapy and Gene Cloning

Gene therapy	Gene cloning
The process of replacing defective gene responsible for hereditary disease by the normal gene is called gene therapy.	The technique to produce identical copies of a particular segment of DNA or a gene.

Question. Explain how a hereditary disease can be corrected. Give an example of first successful attempt made towards correction of such diseases. 
Ans. A hereditary disease can be corrected by gene therapy. In this method, normal genes are inserted into a person’s cells and tissues to treat a disease.
The first successful attempt for gene therapy was done for adenosine deaminase (ADA) deficiency.

Question. What is GEAC and what are its objectives? 
Ans. GEAC (Genetic Engineering Approval Committee) is an Indian government organisation. Its objective are to:
(a) examin ethe validity GofM (Genetic modificatio nof organismr)e search.
(b) inspect the safety of introducing GM for public services and for their large scale use.

Question. A person is born with a hereditary disease, suggest the possible corrective method for it. Illustrate by giving a specific example.
Ans. The possible corrective method is gene therapy.
For example, ADA (Adenosine deaminase) deficiency has been treated through gene therapy.
Lymphocytes from the blood of the patient are grown in a culture. A functional ADA cDNA is introduced into these lymphocytes, which are subsequently returned to the patient. The permanent cure is done by introducing ADA cDNA into cells at early embryonic stages.

Question. Write the functions of adenosine deaminase enzyme. State the cause of ADA deficiency in humans. Mention a possible permanent cure for a ADA deficiency patient. 
Ans. Adenosine deaminase enzyme is responsible for the proper functioning of the immune system.
ADA deficiency is caused by deletion of gene for adenosine deaminase. A possible permanent cure would be gene therapy, if it is detected at early embryonic stage.

Question. How is a mature, functional insulin hormone different from its pro-hormone 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.

Question. Why is the functional insulin thus produced considered better than the ones used earlier by diabetic patients?
Ans. The insulin prepared by rDNA technology does not produce sensitive allergic reactions and immunological reactions whereas those used earlier produced allergic reactions and other complications to the foreign protein as earlier they were extracted from pancreas of slaughtered cattle or pigs.

Question. Why do the toxic insecticidal proteins secreted by Bacillus thuringiensis kill the insect and not the bacteria itself? 
Ans. The Bt toxin protein exists as inactive protoxins but once an insect ingests the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals. Therefore, it does not kill the bacteria.

Question. What is gene therapy? Name the first clinical case where it was used. 
Ans. Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo.
Genes are inserted into an individual’s cells and tissues to treat disease.
The first clinical case where it was used was for caring Adenosine deaminase (ADA) deficiency.

Question. Why is the introduction of genetically engineered lymphocytes into an ADA deficiency patient not a permanent cure? Suggest a possible permanent cure. 
Ans. Introduction of genetically engineered lymphocytes into an ADA deficiency patient is not a permanent cure because these cells are not immortal and the patient requires periodic infusion of such genetically engineered lymphocytes. A possible permanent cure can be isolating the gene producing adenosine deaminase (ADA) from bone marrow cells and introducing it into cells at early embryonic stages.

Question. How have transgenic animals proved to be beneficial in:
(a) Production of biological products?
(b) chemical safety testing? 
Ans. (a) Rosie–the transgenic cow, produced human proteins containing human α-lactalbumin.
Transgenic animals have been made to produce α-1-antitrypsin used to treat emphysema.
(b) Toxicity testing – Transgenic animals are more sensitive to toxic substances, so the results are obtained in less time.

Question. I) Expand GMO . What are the uses of G.M. Pants ?
Ans. Genetically Modified Organism.
i) It tolerates abiotic stresses such as cold ,drought salt & heat.
ii) It reduces reliance / dependence on chemical pesticides
iii) It reduces post harvest loses.
iv) It increases efficiency of mineral utilization by plants.
v) Enhances nutritional value of food

Question. Match the following

A	B
i) Bt toxin	i) Human alpha lactalbumin
ii) CryIAc& cryIIAb	ii)Emphysema
iii) CryIAb	iii) Bacillus thuringiensis
iv) α-1 –antitrypsin	iv) Corn borer
v) Produce of transgenic cow Rosie	v) cotton bollworms

Ans. i) Bt toxin — ——————————— —-Bacillus thuringiensis
ii) CryIAc&  cryIIAb—————————- —–Cotton bollworms i
ii) CryIAb ——————————————– Corn borer
iv)  α-1 –antitrypsin ———————————Emphysema
v) Produce of transgenic cow Rosie ———— Human alpha lactalbumin.

Question. Give one word
i) Supply of alternative resources to industries In the form of starches fuels & pharmaceuticals.
ii New strategy adopted to protect the tobacco Plant infestation by Meloidogyne incognitia.
iii) Technique based on the principle of antigen antibody interaction.
iv) Uses of bioresource by multinational companies/other organization without  proper authorization from the concernedparties.
v) Decision making organization regardingvalidity of G.M resources & the safety of introducing G.M crops.
Answer.i)Supply of alternative resources to industries in the form of starches fuels & pharmaceuticals.        i) Tailor-made plants
ii New strategy adopted to protect the tobacco plant infestation by Meloidogyne incognitia                        ii) RNA interference
iii) Technique based on the principle of antigen antibody interaction                                                              iii) ELISA
iv) Uses of bioresources by multinational companies /other organization whitout proper authorization from the concerned parties iv)Biopiracy
v) Decision making organization regardingvalidity of G.M. resources & the safety of introducing G.M. crops v) GEAC

Question. Differentiate between the insulin produce by rDNA & insulin produce by pancreas.
Ans.
rDNA                                                    Insulin produced by pancreas
i) It is produced artificialy                          i) It is produced naturally
ii) It produces only A & B polypeptides    ii)It has three
polypeptides                                              A,B& C before maturation

Long Answer Questions

Question. Explain the application of biotechnology in producing Bt cotton.
Answer : Bt toxin gene has been cloned from the bacteria,and has been expressed in plants, to provide resistance to insects (without the need for synthetic insecticide). Bt toxin gene forms protein crystals.
These crystals contain a toxic insecticidal protein. Bt toxin protein exists as inactive protoxin in the host, but once the insect ingests the inactive toxin, it is converted into active form of toxin, due to alkaline pH of the gut which solubilises the crystals, causing death of the insect.

Question. What are transgenic animals ? How such animals are helpful to humans ? 
Answer : Transgenic animals are those animals whose genome has been altered by the introduction of an extra gene by manipulation, e.g., transgenic rats,rabbits, sheep, etc. Benefits of transgenic animals are :
(i) Transgenic animals are produced to study how genes are regulated and how they affect the normal functions and development of the animal body.
(ii) Medicines are produced from transgenic animals, e.g., alpha-1-antitrypsin.
(iii) Transgenic animals are used to test vaccine safety before use in humAnswer :
(iv) Transgenic animals are designed to increase our understanding of how genes contribute to the development of diseases.

Question. Describe the various stages involved in gene transfer for the commercial production of human insulin by Eli Lilly.
Ans. (a) Eli Lilly prepared two DNA sequences corresponding to the A and B chains of human insulin.
(b) Sticky ends were produced in the Escherichia coli plasmid and the insulin gene by treating them both with the same restriction endonucleases.
(c) These two are then joined together by the enzyme DNA ligase.
(d) The bacteria are then grown in sterilised bioreactors in the appropriate growth medium.
(e) The chainAs and B aprreoduce dseparately, extracte d and purified.
(f) These two chaairnes the cnombined b y creatin g disulfid beonds to fohrumm an insulin.

Question. Mention some transgenic plants and their potential applications.
Ans. Some transgenic plants and their potential applications

S.No.	Transgenic plants	Useful applications
(i)	Flavr Savr tomato	Better nutrient quality.
(ii)	Brassica napus	Contains hirudin (a protein) that prevents blood clotting. Hirudin is  synthesised chemically and it is transferred into Brassica napus.
(iii)	Bt cotton	It has resistance to bollworm infestation, tolerance to herbicide, high yielding.
(iv)	Wheat	Resistant against herbicide PPT (Commercial name “Basta”—26 per cent PPT).
(v)	Potato	Content of starch increased by about 20–40 per cent.
(vi)	Corn, brinjal	Insect resistance.
(vii)	Maize, soyabean	Herbicide resistance.
(viii)	Golden rice	Rich in vitamin-A.

Question. Recombinant DNA-technology is of great importance in the field of medicine. With the help of a flow chart, show how this technology has been used in preparing genetically engineered human insulin.
Ans.

Question. Plasmid is a boon to biotechnology. Justify this statement quoting the production of human insulin as an example.
Ans. Plasmids are extra-chromosomal, self-replicating, usually circular, double-stranded DNA molecules found naturally in many bacteria.
In 1983, Eli Lilly an American company, first 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. These chains A and B were produced separately, extracted and combined by creating disulfide bonds to form functional human insulin (humulin).

Question. (a) What is gene therapy?
(b) Describe the procedure of such a therapy that could be a permanent cure for a disease.
Name the disease. 
Ans. Gene therapy
• Gene therapy is a collection of methods that allows correction of gene defects, diagnosed in a child or embryo.
• By insertion of normal genes, the defective mutant allele of the genes are replaced and nonfunctional gene is compensated.
• For the first time in 1990, M. Blease and W. F. Andresco of National Institute of Health, attempted gene therapy on a 4 year old girl with adenosine deaminase (ADA) deficiency.
• ADA is caused due to deletion of gene for adenosine deaminase.
• In some cases, it can be cured by bone marrow transplantation and enzyme replacement therapy but it is not fully curative.

Question. (a) Name the deficiency for which first clinical gene therapy was given.
(b) Mention the causes of and one cure for this deficiency. 
Ans. (a) Adenosine deaminase deficiency (ADA).
(b) Cause: Deletion of ADA gene.
Cure: Bone marrow transplantation/enzyme replacement therapy/giving functional ADA to patient by injection/infusion of genetically engineered lymphocytes/introducing gene isolated from marrow cells producing ADA into cells at early embryonic stages. (Any one)

Question. Describe the gene therapy procedure for an ADA-deficient patient. 
Ans. Gene therapy is a method which corrects or replaces the defective genes. In 1900, first clinical gene therapy was given to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme plays an important role in functioning of immune system. This disorder is caused due to the deletion of the gene for adenosine deaminase.

Question. Explain process of gene therapy to treat adenosine deaminase deficiency. Mention two disadvantages of this procedure. 
Ans. (i) Lymphocytes from the blood of the patient are grown on culture outside the body.
(ii) A functional ADA cDNA is then introduced into these lymphocytes using a retroviral vector.
(iii) The genetically engineered lymphocyte are returned to the blood of patient.
Disadvantages: Therapy is not completely curative as cells do not remain alive and periodic infusion of lymphocytes is required.

Question. (a) Name the insect that attacks cotton crops and causes lot of damage to the crop.
How has Bt cotton plants overcome this problem and saved the crop? Explain.
(b) Write the role of gene Cry IAb.
Answer : (a) Cotton bollworm is the larvae that attack cotton crops.
Bt cotton plants are GMOs containing the active Cry gene from Bacillus thuringiensis, which form protein crystals during a particular phase of their growth. These crystals contain a
toxic insecticidal protein.
These proteins are present in inactive protoxin form, but become active toxin in the alkaline pH of the insect gut.
The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis and eventually cause the death of the insect.
Specific Bt toxin genes were isolated from B. thuringiensis and genetically transferred to several crop plants such as cotton.
Most Bt toxins are insect-group specific. The toxin is coded by a gene named cry.
(b) The protein coded by gene cryIAb controls corn borer.

Question. Explain the application of rDNA technology to produce insulin.
Answer : Human insulin is synthesised as a pro-hormone.
The pro-hormone contains an extra C-peptide. The C-peptide is not present in mature insulin and is removed during maturation. Eli-Lilly 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. Chain A and B were produced separately, extracted and combined by creating disulphide bonds to form human insulin.