NCERT Exemplar: Biotechnology & its Applications

MULTIPLE CHOICE QUESTIONS 

Q.1. Bt cotton is not:
(a) A GM plant
(b) Insect resistant
(c) A bacterial gene expressing system
(d) Resistant to all pesticides
Ans: (d)
Explanation:
Bt cotton is a genetically modified crop that carries a gene from the bacterium Bacillus thuringiensis (Bt). This gene enables the plant to produce a specific protein (Bt toxin) that is toxic to certain insect pests, making the crop insect resistant. Options (a), (b) and (c) correctly describe aspects of Bt cotton. However, Bt cotton does not provide resistance to every pesticide or to all pests and diseases; it protects only against particular insect pests targeted by the Bt toxin. Thus option (d) is incorrect and is the right choice for this question.

Q.2. C-peptide of human insulin is:
(a) A part of mature insulin molecule
(b) Responsible for formation of disulphide bridges
(c) Removed during maturation of pro-insulin to insulin
(d) Responsible for its biological activity
Ans: (c)
Explanation:
C-peptide is the short connecting peptide present in the precursor molecule pro-insulin. During conversion to mature insulin, specific proteases cleave and remove the C-peptide, leaving the A and B chains joined by disulphide bridges as the active hormone. The C-peptide itself is not part of the mature insulin responsible for its biological activity, so (c) correctly states its fate.

Q.3. GEAC stands for:
(a) Genome Engineering Action Committee
(b) Ground Environment Action Committee
(c) Genetic Engineering Approval Committee
(d) Genetic and Environment Approval committee
Ans: (c)
Explanation:
GEAC is the regulatory body in India that evaluates activities involving genetically modified organisms. The accepted full form is Genetic Engineering Appraisal Committee. Option (c) is closest to this correct designation and is the intended choice in the question.

Q.4. α - 1 antitrypsin is:
(a) An antacid
(b) An enzyme
(c) Used to treat arthritis
(d) Used to treat emphysema
Ans: (d)
Explanation:
α-1 Antitrypsin is a serum protein that protects lung tissue by inhibiting proteolytic enzymes such as elastase. A deficiency of α-1 antitrypsin leads to unchecked enzyme activity that damages alveolar tissue and results in emphysema. Replacement therapy with α-1 antitrypsin can be used in patients with emphysema caused by this deficiency, making (d) the correct option.

Q.5. A probe which is a molecule used to locate homologous sequences in a mixture of DNA or RNA molecules could be:
(a) A ssRNA
(b) A ssDNA
(c) Either RNA or DNA
(d) Can be ssDNA but not ssRNA
Ans: (c)
Explanation:
In molecular biology, a probe is a single-stranded nucleic acid labelled so it can be detected after hybridising to complementary sequences. Both single-stranded DNA (ssDNA) and single-stranded RNA (ssRNA) probes are routinely used to locate homologous sequences in a sample. Probes are labelled (radioactive, fluorescent, or enzymatic) to allow detection, so option (c) is correct.

Q.6. Choose the correct option regarding Retrovirus:
(a) An RNA virus that synthesises DNA during infection
(b) A DNA virus that synthesises RNA during infection
(c) A ssDNA virus
(d) A dsRNA virus
Ans: (a)
Explanation:
Retroviruses are RNA viruses that use the enzyme reverse transcriptase to synthesise a complementary DNA (cDNA) copy from their RNA genome after entering a host cell. This DNA copy can integrate into the host genome and direct production of viral components. This reverse transcription step distinguishes retroviruses from other virus types, so (a) is correct.

Q.7. The site of production of ADA in the body is:
(a) Erythrocytes
(b) Lymphocytes
(c) Blood plasma
(d) Osteocytes
Ans: (b)
Explanation:
Adenosine deaminase (ADA) is produced primarily by lymphoid cells, especially lymphocytes. ADA plays a crucial role in purine metabolism and is important for normal immune system function. ADA deficiency impairs lymphocyte development and causes severe combined immunodeficiency (SCID), which is why (b) is correct.

Q.8. A protoxin is:
(a) A primitive toxin
(b) A denatured toxin
(c) Toxin produced by protozoa
(d) Inactive toxin
Ans: (d)
Explanation:
A protoxin is an inactive precursor of a toxin. Many organisms synthesise toxins in an inactive form to prevent self-damage; activation then occurs under specific environmental conditions. For example, Bt protoxin produced by Bacillus thuringiensis is activated in the alkaline gut of susceptible insect larvae, making (d) the correct choice.

Q.9. Pathophysiology is the:
(a) Study of physiology of pathogen
(b) Study of normal physiology of host
(c) Study of altered physiology of host
(d) None of the above
Ans: (c)
Explanation:
Pathophysiology is the study of functional changes in an organism that result from disease or injury. It describes how normal physiological processes are altered during disease states, so option (c) correctly defines pathophysiology.

Q.10. The trigger for activation of toxin of Bacillus thuringiensis is:
(a) Acidic pH of stomach
(b) High temperature
(c) Alkaline pH of gut
(d) Mechanical action in the insect gut
Ans: (c)
Explanation:
Bt protoxins are solubilised and activated in the alkaline midgut environment of susceptible insect larvae. The high pH helps solubilise the crystalline protoxin and gut proteases then cleave it to the active toxin, which interacts with gut epithelial cells. Therefore (c) is the correct trigger for activation.

Q.11. Golden rice is:
(a) A variety of rice grown along the yellow river in China

(b) Long stored rice having yellow colour tint

(c) A transgenic rice having gene for β - carotene

(d) Wild variety of rice with yellow coloured grains

Ans: (c)

Explanation:

Golden Rice is a genetically modified rice variety engineered to biosynthesise β-carotene (a precursor of vitamin A) in the endosperm of the grain. The β-carotene gives the grains a yellowish colour and the modification aims to reduce vitamin A deficiency in populations dependent on rice as a staple. Hence option (c) is correct.

Q.12. In RNAi, genes are silenced using:
(a) ss DNA
(b) ds DNA
(c) ds RNA
(d) ss RNA
Ans: (c)
Explanation:
RNA interference (RNAi) is a cellular mechanism in which double-stranded RNA (dsRNA) that matches a target mRNA leads to that mRNA's degradation or translational repression. The dsRNA is processed into short interfering RNAs (siRNAs) that guide the silencing complex to the target mRNA. Thus dsRNA is the trigger for gene silencing, making (c) correct.

Q.13. The first clinical gene therapy was done for the treatment of:
(a) AIDS
(b) Cancer
(c) Cystic fibrosis
(d) SCID (Severe Combined Immuno Deficiency resulting form deficiency of ADA)
Ans: (d)
Explanation:
The first approved clinical gene therapy (1990) was performed on a child with adenosine deaminase (ADA) deficiency, a cause of severe combined immunodeficiency (SCID). The therapy aimed to restore ADA function in the patient's lymphocytes, improving immune competence, so (d) is correct.

Q.14. ADA is an enzyme which is deficient in a genetic disorder SCID. What is the full form of ADA?
(a) Adenosine deoxyaminase
(b) Adenosine deaminase
(c) Aspartate deaminase
(d) Arginine deaminase
Ans: (b)
Explanation:
ADA stands for Adenosine deaminase, an enzyme important in purine metabolism. Its deficiency leads to accumulation of toxic metabolites that impair lymphocyte development and function, causing SCID.

Q.15. Silencing of a gene could be achieved through the use of:
(a) RNAi only
(b) Antisense RNA only
(c) Both RNAi and antisense RNA
(d) None of the above
Ans: (c)
Explanation:
Gene silencing can be achieved by both RNA interference (RNAi) and antisense RNA approaches. RNAi uses double-stranded RNA processed into siRNAs that guide degradation of complementary mRNA. Antisense RNA is single-stranded and complementary to the target mRNA; binding of antisense RNA can block translation or promote degradation. Both methods reduce expression of the target gene, so (c) is correct.

VERY SHORT ANSWER TYPE QUESTIONS

Q.1. In view of the current food crisis, it is said, that we need another green revolution. Highlight the major limitations of the earlier green revolution.
Ans: Limitations of the Green Revolution include:

• The Green Revolution increased food production significantly but often relied on high inputs of fertilisers, irrigation and pesticides; gains were driven largely by management and input use rather than by sustainable genetic improvements, and further increases are limited without new technologies or inputs.
• Extensive use of agrochemicals caused environmental damage, including eutrophication of water bodies and accumulation of toxic substances in ecosystems.
• Irrigation practices led to water-logging and secondary salinisation in certain areas, reducing long-term soil fertility and sustainability of agricultural lands.

Q.2. Expand GMO. How is it different from a hybrid?
Ans: GMO stands for Genetically Modified Organism. A hybrid is produced by sexual crossing between two different strains or species so that the offspring contains a mixture of the parental genomes. In contrast, a GMO is created by introducing specific foreign gene(s) into an organism's genome (or maintaining them extra-chromosomally); only particular genes are transferred rather than whole genomes.

Q.3. Differentiate between diagnostics and therapeutics. Give one example and for each category.
Ans: Diagnostics identify or detect diseases or their causes; for example, ELISA is used to detect HIV infection. Therapeutics treat or manage disease; for example, antibiotics treat bacterial infections.

Q.4. Give the full form of ELISA. Which disease can be detected using it? Discuss the principle underlying the test.
Ans: ELISA stands for Enzyme-Linked ImmunoSorbent Assay. It is commonly used to detect infections such as HIV. The principle is specific antigen-antibody interaction: either antigen from the pathogen or antibody from the host is captured on a solid surface and detected using an enzyme-linked antibody. Addition of the enzyme substrate produces a measurable colour change proportional to the amount of target molecule.

Q.5. Can a disease be detected before its symptoms appear? Explain the principle involved.
Ans: Yes. Early detection is possible by amplifying traces of pathogen nucleic acid using the polymerase chain reaction (PCR). PCR can amplify minute amounts of DNA or RNA from bacteria or viruses to detectable levels before symptoms develop, enabling diagnosis at an early stage of infection.

Q.6. Write a short note on Biopiracy highlighting the exploitation of developing countries by the developed countries.
Ans: Biopiracy refers to the unauthorised or unfair commercial use of biological resources and associated traditional knowledge from developing countries by external entities. Companies may obtain patents or commercial products derived from indigenous plants, genes or practices without prior informed consent or fair benefit sharing. This results in loss of rights and economic benefits for source communities. To combat biopiracy, countries maintain legal protections, documentation of traditional knowledge and regulations for access and benefit sharing.

Q.7. Many proteins are secreted in their inactive form. This is also true of many toxic proteins produced by micro organisms. Explain how the mechanism is useful for the organism producing the toxin?
Ans: Secreting proteins as inactive precursors (protoxins or pro-enzymes) prevents the producing organism from self-damage. Activation occurs only under specific triggers such as a change in pH, presence of host proteases or temperature. For example, Bt protoxin remains inactive within Bacillus thuringiensis and becomes activated only in the alkaline gut of susceptible insects, protecting the bacterium while allowing the toxin to act on the target insect.

Q.8. While creating genetically modified organisms, genetic barriers are not respected. How can this be dangerous in the long run?
Ans: Ignoring natural genetic barriers can create organisms with novel traits that may have unpredictable ecological effects when released. Potential long-term dangers include gene flow to wild relatives, loss of biodiversity, disruption of ecosystems, evolution of resistant pests or pathogens, and unintended effects on non-target species. Careful risk assessment, containment and regulation are therefore essential before releasing GM organisms.

Q.9. Why has the Indian Parliament cleared the second amendment of the country's patents bill?
Ans: The second amendment to the Indian Patents Bill addressed patent term provisions, emergency use clauses and aims to balance intellectual property protection with public interest. The amendments sought to promote research and development while ensuring that patents do not unduly restrict access to essential technologies and that local innovation is encouraged.

Q.10. Give any two reasons why the patent on Basmati should not have gone to an American Company.
Ans:
(i) Basmati rice has a long cultural and agricultural history in South Asia, with many locally developed cultivars; granting exclusive foreign patents over such traditional varieties without recognition or compensation would be unjust.
(ii) There is extensive prior knowledge, historical reference and local diversity associated with Basmati. Awarding exclusive rights to an external company could deprive local communities and farmers of benefits and contravene principles of prior art and traditional knowledge protection.

Q.11. How was Insulin obtained before the advent of rDNA technology? What were the problems encountered?
Ans: Before recombinant DNA technology, insulin was extracted from the pancreases of slaughtered cattle and pigs. Problems included limited supply that required large numbers of animals, risk of immune reactions in some patients due to minor differences from human insulin, ethical concerns over animal slaughter and the potential for contamination if purification was inadequate.

Q.12. With respect to understanding diseases, discuss the importance of transgenic animal models.
Ans: Transgenic animals carry introduced genes and are valuable for modelling human diseases. They help researchers study how specific genes influence development, physiology and disease processes, enabling investigation of disease mechanisms, progression and testing of potential therapies in a whole-organism context. Examples include models for cancer, cystic fibrosis and neurodegenerative disorders.

Q.13. Name the first transgenic cow. Which gene was introduced in this cow?
Ans: The first transgenic cow named Rosie was engineered to express the human milk protein α-lactalbumin in its milk. This modification aimed to improve the nutritional profile of the milk.

Q.14. PCR is a useful tool for early diagnosis of an infectious disease. Elaborate.
Ans: Polymerase Chain Reaction (PCR) is a highly sensitive method that can amplify specific DNA sequences from tiny amounts of starting material. Because of this sensitivity and specificity, PCR can detect the presence of an infectious organism very early in infection - often before symptoms appear and before the organism has multiplied to large numbers - enabling prompt and accurate diagnosis.

Q.15. What is GEAC and what are its objectives?
Ans: GEAC stands for Genetic Engineering Appraisal Committee. It is an Indian regulatory authority that evaluates proposals involving genetically modified organisms. Its main objectives are:
(a) To examine and appraise research and development activities involving genetic modification for safety and compliance.
(b) To assess environmental and public health safety before granting approval for release or commercial use of GM organisms.

Q.16. For which variety of Indian rice, the patent was filed by a USA Company?
Ans: A patent application filed by a USA company related to a variety derived from Indian Basmati rice that had been crossed with a semi-dwarf variety; this claim generated controversy because Basmati has well-established traditional and agricultural roots in India.

Q.17. Discuss the advantages of GMO.
Ans: Genetically Modified Organisms (GMOs) offer several benefits:

1. Improved tolerance to abiotic stresses (drought, salinity, cold, heat), helping maintain yields under adverse conditions.
2. Reduced reliance on chemical pesticides by introducing pest-resistance traits, lowering environmental harm.
3. Decreased post-harvest losses by making crops less susceptible to spoilage and pests.
4. Improved nutrient and mineral use efficiency in plants, conserving soil fertility.
5. Enhanced nutritional value of crops (for example, β-carotene in Golden Rice to address vitamin A deficiency).

Additionally, GM technology enables development of plants tailored for industrial uses such as specialised starches, biofuels and pharmaceutical protein production.

SHORT ANSWER TYPE QUESTIONS

Q.1. Gene expression can be controlled with the help of RNA. Explain the method with an example.
Ans: RNA interference (RNAi) is a method to silence gene expression. A double-stranded RNA complementary to the target mRNA is introduced into the cell. Cellular enzymes process the dsRNA into short interfering RNAs (siRNAs) that guide the silencing complex to the target mRNA, leading to its degradation and preventing translation. An example is using RNAi to provide resistance in tomato plants against the root-knot nematode Meloidogyne incognita by targeting essential nematode genes.

Q.2. Ignoring our traditional knowledge can we prove costly in the area of biological patenting. Justify.
Ans: Yes. Traditional knowledge and local biodiversity often contain valuable information that can lead to new products. If this knowledge is ignored, foreign entities may patent products or methods derived from it without compensating source communities. This results in economic loss and unfair appropriation. Documentation, legal protection and benefit-sharing agreements help prevent such biopiracy.

Q.3. Highlight any four areas where genetic modification of plants has been useful.
Ans: Genetic modification of plants has been useful in:
(i) Improving tolerance to abiotic stresses (drought, salinity, cold, heat).
(ii) Reducing dependence on chemical pesticides by developing pest-resistant crops.
(iii) Decreasing post-harvest losses through improved resistance to spoilage and pests.
(iv) Enhancing efficiency of mineral and nutrient use by plants, aiding soil fertility conservation.

Q.4. What is a recombinant DNA vaccine? Give two examples.
Ans: A recombinant DNA vaccine is produced by inserting the gene encoding an antigen into an expression system (bacteria, yeast or viral vector) to produce the antigenic protein, which is then used as a vaccine. Examples include the hepatitis B vaccine produced in yeast and some recombinant subunit vaccines developed for other viral diseases.

Q.5. Why is it that the line of treatment for a genetic disease is different from infectious diseases?
Ans: Genetic diseases arise from inherited defects in genes and require approaches that correct or compensate for the faulty gene or its product (for example, gene therapy or enzyme replacement). Infectious diseases are caused by external pathogens and are treated by removing or inhibiting the pathogen (antibiotics, antivirals, vaccines). Thus the root causes differ and so do treatment strategies.

Q.6. Discuss briefly how a probe is used in molecular diagnostics.
Ans: A probe is a single-stranded DNA or RNA molecule labelled with a detectable marker. It hybridises to complementary sequences in a sample or clone. After hybridisation, detection is achieved by autoradiography for radioactive probes or by colour/fluorescent detection for non-radioactive probes, revealing the presence or absence of the target sequence. Probes enable identification of specific genes or mutations in diagnostic assays.

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 (1990) was given to a four-year-old girl with adenosine deaminase (ADA) deficiency. In that early approach, the patient's lymphocytes were removed, modified ex vivo to express functional ADA, and reinfused. Because the modified lymphocytes were not permanently self-renewing in the patient, repeated infusions were required over time; therefore the treatment was recurrent rather than a single permanent cure.

Q.8. Taking examples under each category, discuss upstream and downstream processing.
Ans: Upstream processing: Includes gene isolation, vector construction, cell line development and culture expansion to express the desired product.
Downstream processing: Involves recovery, separation and purification of the product (for example, chromatographic steps), formulation with excipients, quality control testing and regulatory procedures before the final product is released. Upstream creates the biological product; downstream converts it into a safe, pure and usable form.

Q.9. Define Antigen and Antibody. Name any two diagnostic kits based upon them.
Ans: An antigen is a foreign molecule (often a protein) that elicits a specific antibody response. An antibody is a protein produced by the immune system that recognises and binds specifically to its antigen. Two diagnostic kits based on antigen-antibody interaction are:
(a) ELISA for detection of HIV antibodies.
(b) Home pregnancy test kits that detect the human chorionic gonadotropin (hCG) antigen.

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. If a genetic disorder leads to absence or markedly reduced levels of a specific protein or enzyme, ELISA can detect that change by using antibodies against the protein. For example, antibodies against the enzyme that metabolises phenylalanine could be used to develop an ELISA to detect individuals lacking the enzyme protein; low or absent signal compared with normal controls would indicate the disorder.

Q.11. How is a mature, functional insulin hormone different from its prohormone form?
Ans: Mature insulin is produced from pro-insulin by proteolytic removal of the connecting peptide called C-peptide. Pro-insulin contains the A and B chains plus the C-peptide; removal of the C-peptide yields the mature biologically active insulin composed of A and B chains linked by disulphide bridges.

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: Gene therapy has the potential to provide a long-term or permanent correction if a functional gene is stably introduced into appropriate cells (particularly stem cells). Enzyme replacement therapy supplies the missing protein but is temporary and requires repeated administrations. Although gene therapy presents technical and safety challenges, it may offer a more lasting solution, while enzyme replacement therapy is often used for ongoing management.

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: For studying basic biological processes, transgenic mice carrying reporter genes (for example, GFP fusions) are widely used. For producing useful products, the transgenic cow Rosie, engineered to express human α-lactalbumin in milk, is an example of altering animal products for human benefit.

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: Introduced DNA is often carried on a plasmid vector that replicates in the host and is partitioned into daughter cells during cell division. For stable inheritance by progeny, the foreign DNA is integrated into the host genome or introduced into germline cells so that it is passed on during reproduction.

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 expresses Bt toxin that targets specific insect pests (mainly certain Lepidoptera and some other susceptible groups). It does not provide resistance to all pests, pathogens or abiotic stresses. Other insect species, fungal or bacterial diseases and environmental factors can still affect Bt cotton, so integrated pest management practices remain necessary.

LONG ANSWER QUESTIONS 

Q.1. A patient is suffering from ADA deficiency. Can he be cured? How?
Ans: Several therapeutic approaches exist for ADA deficiency:

1. Bone marrow transplantation from a compatible donor can reconstitute the immune system and restore ADA activity in some patients.
2. Enzyme replacement therapy supplies functional ADA protein by regular injections; this manages the disease but is not usually curative and requires ongoing treatment.
3. Gene therapy aims to introduce a functional ADA gene into the patient's cells. Early clinical approaches involved removing the patient's lymphocytes, transducing them ex vivo with a viral vector carrying ADA cDNA, and reinfusing them. This can improve immune function, but long-term cure requires stable correction of hematopoietic stem cells so that corrected cells persist lifelong.

Q.2. Define transgenic animals. Explain in detail any four areas where they can be utilised.
Ans: Transgenic animals carry one or more genes from another species introduced by genetic engineering that are expressed in the host. Four major uses are:

1. To study normal physiology and development: By overexpressing or knocking out specific genes, researchers learn when and where genes act during growth and differentiation.
2. Study of diseases: Transgenic animals can model human diseases (for example, cancer, Parkinson's disease) to identify disease mechanisms and test therapies.
3. Vaccine and drug testing: Transgenic models help evaluate safety and efficacy of vaccines and therapeutics in a whole-organism setting before clinical trials.
4. Chemical safety testing: Animals engineered to be more sensitive to particular chemicals or toxins allow faster and more reliable assessment of toxic effects and side effects, improving safety evaluation.

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 bacterial gene, the typical steps are:
(1) Isolation of the desired gene using restriction endonucleases.
↓
(2) Ligation of the gene into a suitable vector to create recombinant DNA.
↓
(3) Introduction of the recombinant DNA into plant cells using an appropriate DNA delivery method (for example, Agrobacterium-mediated transfer, gene gun or electroporation).
↓
(4) Screening and selection of transformed cells using selectable markers.
↓
(5) Regeneration of whole plants from transformed cells via tissue culture to obtain transgenic plants expressing the introduced gene.

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

1. Therapeutics and diagnostics (production of drugs, vaccines and diagnostic kits).
2. Genetically modified crops for agriculture (improved yield, pest resistance, stress tolerance).
3. Processed food (use of enzymes and microbial processes in food production).
4. Bioremediation (use of organisms to remove pollutants from environments).
5. Waste treatment and energy production (microbial treatment of wastes and biofuel production).

Q.5. What are the various advantages of using genetically modified plants to increase the overall yield of the crop?
Ans: Genetically modified plants can:

1. Be more tolerant to abiotic stresses (cold, drought, salinity, heat), helping maintain yields under adverse conditions.
2. Reduce dependence on chemical pesticides by incorporating pest-resistance traits.
3. Reduce post-harvest losses through enhanced resistance to spoilage and pests.
4. Improve nutrient and mineral use efficiency, reducing depletion of soil fertility.
5. Enhance nutritional value (for example, vitamin A enrichment in Golden Rice).

Additionally, GM technology allows development of plants tailored for industrial uses such as specialised starches, biofuels and production of pharmaceutical proteins.

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: The Bt toxin gene from Bacillus thuringiensis has been introduced into crops such as Bt cotton and Bt maize. Plants expressing Bt toxin are resistant to particular insect pests and therefore reduce the need for chemical insecticide sprays.
(b) Enhance nutritional value of food crops: Golden Rice has been engineered to synthesise β-carotene (a precursor of vitamin A) in the grain to address vitamin A deficiency in populations dependent on rice as a staple food.

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

1. Insulin yields from animal pancreases were low, so many animals had to be slaughtered to obtain clinically useful quantities, increasing cost and raising ethical concerns.
2. Animal-derived insulin differs slightly from human insulin and can cause immune reactions or allergic responses in some patients.
3. There is risk of contamination with infectious agents from animal tissues if purification is inadequate.

Q.8. List the advantages of recombinant insulin.
Ans: Recombinant human insulin produced in bacterial or yeast systems offers these advantages:
- It is identical or very similar to human insulin, reducing the risk of immune reactions.
- Production is scalable and independent of animal slaughter, improving supply and ethical acceptability.
- Purity and batch-to-batch consistency are higher, meeting large clinical demand reliably.

Q.9. What is meant by the term bio-pesticide? Name and explain the mode of action of a popular bio-pesticide.
Ans: A bio-pesticide is a pest control agent derived from natural sources (microorganisms, their metabolites or natural products), typically more specific to target pests and less harmful to the environment than broad-spectrum chemical pesticides. A widely used example is the Bt toxin from Bacillus thuringiensis. Bt protoxin is ingested by target insect larvae; the alkaline gut conditions solubilise and proteases activate the protoxin to the toxin, which binds to receptors on midgut epithelial cells, forms pores, causes cell lysis and gut paralysis, and eventually leads to death of the insect. Bt can be applied as a spray or expressed in transgenic crops.

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: Enzymes that cut DNA at specific recognition sequences to isolate desired fragments.
2. Gel electrophoresis: Technique used to separate DNA fragments by size for analysis and isolation.
3. DNA ligase: Enzyme that joins DNA fragments to form recombinant DNA molecules.
4. DNA delivery systems: Methods such as electroporation, microinjection, gene gun or Agrobacterium-mediated transfer used to introduce recombinant DNA into host cells.
5. Competent host cells: Organisms (bacterial, yeast, plant or animal cells) that accept and express recombinant DNA, allowing propagation and production of the desired product.