CBSE Important Questions Class 12 Biology Chapter 10 – Biotechnology and its Applications

Class 12 Biology Chapter 10 Biotechnology and its Applications is the tenth chapter of the NCERT Class 12 Biology textbook. It explains how biotechnology is used in agriculture and medicine: genetically modified crops such as Bt cotton, pest-resistant plants made by RNA interference (RNAi), genetically engineered insulin, gene therapy for ADA deficiency, molecular diagnosis using PCR and ELISA, transgenic animals, and the ethical issues and biosafety rules controlled by GEAC in India.

These CBSE important questions for Class 12 Biology Chapter 10 cover Taq polymerase and the gene therapy for ADA deficiency, the plasmid as a vector, the role of GEAC and the ethical issues of GM crops, RNA interference in tobacco, the Cry genes and the action of Bt toxin in Bt cotton, and reading the results of a mutant-specific PCR test. The set has multiple-choice, short-answer and case-based questions with answers for board exam revision.

Q1. (a) Name the source of Taq polymerase. Explain the advantage of its use in biotechnology.
(b) Expand the name of the enzyme ADA. Why is this enzyme essential in the human body? Suggest the gene therapy for its deficiency.

Answer: (a) Taq polymerase is obtained from the thermophilic bacterium Thermus aquaticus. In biotechnology, it is used in the polymerase chain reaction (PCR) for making many copies of a segment of DNA. Taq polymerase is heat-stable: it can tolerate the high temperature used during the denaturation step of PCR, so DNA can be amplified cycle after cycle without adding fresh enzyme.
(b) ADA stands for Adenosine Deaminase. ADA is essential for the proper functioning of the immune system of the body. Its deficiency can be cured by gene therapy as follows:
1. Lymphocytes are taken from the blood of the patient suffering from ADA deficiency and grown in a culture medium.
2. A functional ADA cDNA (using a retroviral vector) is introduced into these lymphocytes.
3. The lymphocytes containing the ADA cDNA are then returned to the body of the patient. The patient is now able to produce the ADA enzyme, but as these cells are not immortal, the patient needs periodic infusion of such genetically engineered lymphocytes. If the gene is introduced into cells at an early embryonic stage, it could be a permanent cure.

Q2. The label ‘A’ is an important part of the bacterial cell. What role does it play in biotechnology?

Bacterial cell showing bacterial DNA and plasmids, with a plasmid labelled A

(a) It is a vehicle for the insertion of recombinant DNA into bacteria.
(b) It acts as a recognition site on recombinant DNA strands.
(c) It is used for protein synthesis in eukaryotic recombinants.
(d) It acts as proviruses incorporated into the host DNA.

Answer: (a) It is a vehicle for the insertion of recombinant DNA into bacteria.
Label ‘A’ is a plasmid, an extra-chromosomal circular DNA present in bacteria. Plasmids replicate on their own and often carry antibiotic resistance genes that are used as selectable markers. In biotechnology, plasmids serve as vectors: the gene of interest is cut and ligated into the plasmid, the recombinant plasmid is put into competent bacterial cells (transformation), and the transformed bacteria multiply the plasmid and express the inserted gene.

Q3. The use of genetically modified organisms requires strict monitoring in India.
3.1. What is GEAC and what role does it play in regulating genetically engineered products in the country?
3.2. Explain why the release of genetically modified crops into the environment needs careful scientific evaluation.
3.3. Discuss any two major ethical issues associated with the application of biotechnology, especially in the context of genetically modified organisms.

Answer: 3.1. GEAC (Genetic Engineering Approval Committee) is an Indian regulatory body under the Ministry of Environment, Forest and Climate Change. It evaluates, approves and monitors research, field trials and the commercial release of genetically engineered organisms. GEAC makes sure that the use of GMOs is safe for humans, animals and the environment, and it can change or cancel an approval if any risk is found.
3.2. The release of GM crops requires careful evaluation because they may affect natural ecosystems, non-target organisms or cause unintended changes in biodiversity. They also need to be checked for possible allergenic effects, development of resistance in pests, or transfer of the inserted gene to wild relatives. Proper testing ensures that only safe and stable GM varieties are introduced for cultivation.
3.3. One ethical issue is the concern over food safety, as people may fear that GM foods could have unknown long-term effects on health. Another ethical issue relates to the ownership and patenting of genetic material (biopiracy). Patenting may allow companies to control seeds and biological resources, which can affect farmers' rights and access. These concerns highlight the need for transparent regulations and responsible use of biotechnology.

Q4. RNA interference (RNAi) is widely used for developing pest-resistant plants such as tobacco.
4.1. What is RNA interference and why is it considered an important method of pest control in plants?
4.2. Explain how introducing double-stranded RNA (dsRNA) into a tobacco plant helps protect it from a specific pest.
4.3. Describe, in simple steps, how RNAi stops the expression of the target gene after the pest feeds on the transgenic tobacco plant.

Answer: 4.1. RNA interference is a natural process in which double-stranded RNA prevents the expression of a specific gene by destroying its mRNA (silencing the gene). It is useful in pest control because it blocks essential genes in insect pests or nematodes, reducing their ability to survive, and it avoids the harmful effects of chemical pesticides because it is specific to the target pest.
4.2. A dsRNA sequence that matches an important gene of the pest (for example, the nematode Meloidogyne incognita) is introduced into the tobacco plant through genetic engineering (using Agrobacterium vectors). The plant produces this dsRNA in its tissues. When the pest feeds on the plant, it takes in the dsRNA, which silences the matching gene inside the pest. The pest cannot survive or develop properly, so the plant is protected.
4.3. After the pest consumes the dsRNA, the dsRNA is cut into small RNA fragments called siRNAs. These siRNAs guide a protein complex (RISC) to the pest's mRNA that matches their sequence. The mRNA is then broken down, so the protein encoded by that gene cannot be made. Without this essential protein, the pest cannot survive or develop properly.

Q5. Bt cotton is one of the most widely used genetically modified crops developed for pest resistance.
5.1. What is Bt cotton and why was it developed?
5.2. Mention any two types of Cry genes used in Bt crops and the specific pests they target.
5.3. Explain how the Bt toxin produced in Bt cotton kills insect pests, describing the steps involved in its action.

Answer: 5.1. Bt cotton is a genetically modified cotton variety that contains a gene from the bacterium Bacillus thuringiensis (Bt). It was developed to provide resistance against the major cotton pests, especially bollworms, which cause severe damage and reduce yield. By producing the Bt toxin inside its tissues, the plant gains protection without repeated spraying of chemical pesticides.
5.2. Different Cry genes are used depending on the target pest. cryIAc and cryIIAb control the cotton bollworms, while cryIAb controls the corn borer. These genes enable the plant to produce proteins that are toxic to these specific insect groups.
5.3. The Bt toxin is produced in an inactive protoxin form inside the plant. When an insect larva eats Bt cotton leaves, the alkaline pH of its gut converts the protoxin into the active toxin. The activated toxin binds to specific receptors on the midgut epithelial cells of the insect. This creates pores in the gut lining, causing swelling and lysis of the cells, leakage of gut fluids and finally the death of the larva. The toxin is harmless to humans and other animals because it needs the alkaline gut and the insect-specific receptors to act.

Q6. A diagnostic laboratory used PCR to detect a cancer-associated mutation in DNA samples from three patients. The results of the mutant-specific PCR are shown below.

Sample Mutant-specific PCR band
A Strong band
B Weak band
C No band

6.1. Based on the data, which sample(s) are positive for the mutation? Give two reasons.

Answer: 6.1. Samples A and B are positive for the cancer-associated mutation; sample C is negative.
Reason 1: A PCR band appears only when the mutant-specific primers find and amplify the mutant DNA sequence. Samples A and B show a band, so the mutant DNA is present in both; sample C shows no band, so the mutant DNA is absent.
Reason 2: The band intensity reflects the amount of mutant DNA. Sample A has a strong band (a large amount of mutant DNA, clearly positive), while sample B has a weak band (a small amount of mutant DNA, so it is also positive, though mildly).

Related Study Material on Extramarks