Chapter 10: Biotechnology and its Applications Case Study Questions | biology Class 12 CBSE

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Chapter 10: Biotechnology and its Applications Case Study Questions | biology Class 12 CBSE | ByteNotes.in

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A farmer in Punjab noticed that his cotton crop was being severely damaged by bollworms every season, leading to huge economic losses. Despite repeated spraying of chemical insecticides, the pest population was not controlled effectively. A biotechnology scientist visited the farm and suggested switching to Bt cotton. She explained that certain strains of Bacillus thuringiensis produce crystalline proteins during a specific phase of growth. When incorporated into cotton plants via genetic engineering, these proteins protect the crop from lepidopteran pests. The scientist further clarified that the toxin is harmless to the plant itself and becomes active only inside the insect gut due to specific pH conditions, eventually causing cell lysis and death of the pest.

Question 1: Name the toxic protein produced by Bacillus thuringiensis and state why it does not kill the bacterium itself.

The toxic protein is called Bt toxin (cry protein), which exists as an inactive protoxin inside the bacterium.
It does not kill the bacterium because the protoxin is inactive; it is only activated in the alkaline pH of the insect midgut.

Question 2: Explain the mechanism by which activated Bt toxin kills the target insect.

Once ingested, the alkaline pH of the insect gut solubilises the crystal and converts the inactive protoxin into an active form.
The activated toxin binds to epithelial cells of the midgut, creates pores, causes cell swelling and lysis, ultimately killing the insect.

Question 3: Name two specific cry genes and their target pests. Also explain why Bt crops are considered environmentally safer than chemical pesticides.

cryIAc and cryIIAb control cotton bollworms; cryIAb controls corn borer.
Bt toxins are insect-group specific, so they do not harm non-target organisms.
They reduce the need for broad-spectrum chemical pesticides, thereby decreasing chemical pollution of soil and water.
Being biodegradable proteins, they leave no toxic residues in the environment.

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Case Set 2

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A research team studying tobacco plant diseases noticed that a particular crop field showed significantly reduced yields due to nematode infestation. The nematode Meloidogyne incognita was found to be parasitising the roots extensively. The scientists decided to use RNA interference (RNAi) as a novel biotechnological strategy to protect the plants. Using Agrobacterium as a vector, they introduced nematode-specific gene sequences into the tobacco plants in such a way that both sense and antisense RNA strands were produced in the host cells. The resulting double-stranded RNA silenced the corresponding mRNA in the nematode, preventing its survival. The transgenic plants showed significantly improved resistance to nematode infestation in subsequent experiments.

Question 1: What is RNA interference (RNAi) and which organism was used as a vector to introduce the gene in the tobacco plant?

RNAi is a cellular defense mechanism in eukaryotes involving silencing of specific mRNA by a complementary dsRNA molecule that prevents its translation.
Agrobacterium was used as a vector to introduce nematode-specific gene sequences into the tobacco plant.

Question 2: Explain how dsRNA formation in the host plant protects it against the nematode Meloidogyne incognita.

The introduced DNA produced both sense and antisense RNA in the host cells.
These complementary strands annealed to form dsRNA, which initiated RNAi, silencing the nematode-specific mRNA and preventing the nematode from surviving inside the transgenic plant.

Question 3: Describe the natural sources of dsRNA in eukaryotic cells and explain the significance of RNAi as a tool in crop protection, giving its advantages over chemical nematicides.

Natural sources of dsRNA in cells include RNA viruses (with RNA genomes) and mobile genetic elements (transposons) that replicate via RNA intermediates.
RNAi-based crop protection is species-specific, targeting only the nematode without harming the plant or other soil organisms.
It eliminates the need for chemical nematicides, which are often toxic, non-biodegradable and environmentally harmful.
The strategy is heritable in transgenic lines, providing durable resistance across generations.

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Case Set 3

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A diabetic patient in the 1970s was dependent on insulin extracted from the pancreas of slaughtered cattle and pigs. Although effective, this insulin sometimes caused allergic reactions because it was a foreign protein. Scientists recognised the need for human insulin that would be identical in structure to the body's own insulin, thereby avoiding immune responses. In 1983, the American company Eli Lilly achieved a breakthrough by separately producing the A and B chains of human insulin in E. coli using recombinant DNA technology. The two chains were then extracted and combined through the formation of disulphide bonds to yield functional human insulin, which has since revolutionised diabetes management worldwide.

Question 1: Why was animal-derived insulin replaced by recombinant human insulin? Give two reasons.

Animal insulin sometimes caused allergic reactions or other immune responses as it was a foreign protein to the human body.
Recombinant human insulin is structurally identical to natural human insulin and does not trigger unwanted immunological responses.

Question 2: Describe the structure of insulin and explain the main challenge faced in producing it using rDNA technology.

Insulin consists of two short polypeptide chains, chain A and chain B, linked by disulphide bridges.
The main challenge was assembling the two chains into a mature functional form, as the natural insulin is derived from pro-insulin by removal of the C peptide, a step not possible directly in bacteria.

Question 3: Explain the stepwise production of recombinant human insulin by Eli Lilly in 1983. Why cannot insulin be administered orally to diabetic patients?

Two DNA sequences corresponding to insulin chains A and B were synthesised separately and introduced into plasmids of E. coli.
E. coli produced chain A and chain B separately; these were then extracted and purified.
Disulphide bonds were created between the chains in vitro to form functional human insulin.
Insulin cannot be administered orally because being a protein, it would be digested by proteases present in the gastrointestinal tract before it could be absorbed into the bloodstream.

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Case Set 4

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A four-year-old child was diagnosed with severe combined immunodeficiency (SCID) caused by the absence of the enzyme adenosine deaminase (ADA). The child was highly susceptible to infections and could not survive in a normal environment. The physicians decided to attempt gene therapy. Lymphocytes were isolated from the child's blood, and a functional ADA gene was introduced into these cells using a retroviral vector. The genetically modified lymphocytes were then infused back into the child. However, since the lymphocytes are not immortal, the therapy needs to be repeated periodically. Scientists are now trying to introduce the ADA gene into cells at an early embryonic stage to achieve a permanent cure.

Question 1: What is gene therapy? What type of vector was used to introduce the ADA gene into lymphocytes?

Gene therapy is the insertion of functional genes into an individual's cells and tissues to treat diseases, especially hereditary diseases, by replacing a defective or absent allele.
A retroviral vector was used to introduce the functional ADA gene into the patient's lymphocytes.

Question 2: Why does ADA gene therapy using lymphocytes not provide a permanent cure? What approach could lead to a permanent solution?

Lymphocytes are not immortal; they have a limited lifespan, so the gene-corrected cells eventually die, requiring repeated infusions.
A permanent cure would require introducing the ADA gene into bone marrow stem cells or early embryonic cells, which are self-renewing and can produce functional lymphocytes throughout the patient's life.

Question 3: Describe the general principle of gene therapy using viruses as vectors. What are the ethical concerns associated with germ-line gene therapy?

Viruses naturally insert their genetic material into host cells as part of their replication cycle; scientists exploit this by replacing viral genes with therapeutic genes, creating viral vectors that deliver the functional gene into patient cells.
In germ-line gene therapy, changes are made to eggs, sperm, or early embryos, meaning the genetic modification is heritable and passed to future generations.
Ethical concerns include the possibility of unintended genetic alterations being inherited, eugenics-related misuse (designer babies), lack of consent from future individuals, and unpredictable long-term effects on the gene pool.
Such interventions raise questions about 'playing God' and social equity in access to genetic treatments.

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Case Set 5

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A biotechnology company developed transgenic mice that carry a mutated human gene associated with cancer. These mice developed tumours under controlled conditions, making them ideal models to study the progression of cancer and to test new anti-cancer drugs. The researchers also developed transgenic animals that produced human proteins in their milk, such as alpha-1-antitrypsin, useful in treating emphysema. Another group used transgenic pigs with human-compatible cell surface proteins for studying organ transplantation. All these developments highlighted the versatility of transgenic animals in biomedical research, though they also raised significant ethical questions about animal welfare.

Question 1: What are transgenic animals? Give one example of a transgenic animal used in biomedical research.

Transgenic animals are animals that have had their genome altered by introduction of a foreign gene (transgene) using recombinant DNA technology.
Example: Transgenic mice carrying mutated human cancer genes are used as disease models to study cancer progression and test anti-cancer drugs.

Question 2: Explain how transgenic animals are used to produce biologically important proteins, giving one example.

Transgenic animals are engineered to carry human genes that direct production of useful proteins, often secreted in their milk for easy large-scale collection.
Example: Transgenic sheep produce alpha-1-antitrypsin in their milk, which is used to treat emphysema in humans.

Question 3: List three uses of transgenic animals in scientific research and discuss the major ethical concerns associated with their use.

Uses: (i) As disease models – transgenic animals carrying human disease genes help study genetic disorders like cancer, Alzheimer's, and cystic fibrosis. (ii) For production of biological products – human proteins like insulin, clotting factors, and alpha-1-antitrypsin in animal milk. (iii) For vaccine safety testing and chemical safety testing, replacing large numbers of non-transgenic animals.
Ethical concerns include subjecting animals to pain and suffering for human benefit, questions about animal rights and welfare, and genetic manipulation that may cause unforeseen suffering.
There are also concerns about accidental release of transgenic animals into the environment, potentially disrupting ecosystems.

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Chapter 10: Biotechnology and its Applications | Case Study Questions

Passage

Question 1: Name the toxic protein produced by Bacillus thuringiensis and state why it does not kill the bacterium itself.

Question 2: Explain the mechanism by which activated Bt toxin kills the target insect.

Question 3: Name two specific cry genes and their target pests. Also explain why Bt crops are considered environmentally safer than chemical pesticides.

Passage

Question 1: What is RNA interference (RNAi) and which organism was used as a vector to introduce the gene in the tobacco plant?

Question 2: Explain how dsRNA formation in the host plant protects it against the nematode Meloidogyne incognita.

Question 3: Describe the natural sources of dsRNA in eukaryotic cells and explain the significance of RNAi as a tool in crop protection, giving its advantages over chemical nematicides.

Passage

Question 1: Why was animal-derived insulin replaced by recombinant human insulin? Give two reasons.

Question 2: Describe the structure of insulin and explain the main challenge faced in producing it using rDNA technology.

Question 3: Explain the stepwise production of recombinant human insulin by Eli Lilly in 1983. Why cannot insulin be administered orally to diabetic patients?

Passage

Question 1: What is gene therapy? What type of vector was used to introduce the ADA gene into lymphocytes?

Question 2: Why does ADA gene therapy using lymphocytes not provide a permanent cure? What approach could lead to a permanent solution?

Question 3: Describe the general principle of gene therapy using viruses as vectors. What are the ethical concerns associated with germ-line gene therapy?

Passage

Question 1: What are transgenic animals? Give one example of a transgenic animal used in biomedical research.

Question 2: Explain how transgenic animals are used to produce biologically important proteins, giving one example.

Question 3: List three uses of transgenic animals in scientific research and discuss the major ethical concerns associated with their use.

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