UPSC CSE Prelims
Biotechnology Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

All three statements regarding genome editing and stem cell technologies are scientifically correct and represent current capabilities in biotechnology.

✅ Statement 1 – Correct: Germline gene editing using technologies like CRISPR-Cas9 can introduce genetic changes in germ cells (eggs or sperm), making these modifications heritable and transmissible to future generations.

✅ Statement 2 – Correct: Genome editing can be performed at the early embryonic stage (zygote or blastocyst stage) before birth, allowing for correction of genetic mutations that cause hereditary diseases.

✅ Statement 3 – Correct: Human induced pluripotent stem cells (hiPSCs) can be injected into pig embryos to create human-animal chimeras, a technique used in research for studying organ development and exploring potential for human organ transplantation.

📝 Short Notes: Genome Editing and Stem Cell Technologies

• CRISPR-Cas9: A revolutionary gene-editing tool that allows precise modifications to DNA sequences in living organisms, enabling targeted correction of genetic defects.
• Germline Editing: Modifications made to germ cells (eggs, sperm) or early embryos that are heritable and passed to future generations, raising significant ethical concerns.
• Somatic Gene Editing: Changes made to non-reproductive cells that affect only the individual and are not passed to offspring.
• Induced Pluripotent Stem Cells (iPSCs): Adult cells reprogrammed to an embryonic-like pluripotent state, capable of differentiating into any cell type in the body.
• Chimeras: Organisms containing cells from two different species; human-animal chimeras are used in research to study disease mechanisms and organ development.
• Ethical Concerns: Germline editing and chimera research raise questions about human dignity, unintended consequences, equity in access, and the creation of designer babies.
• Regulatory Status: Many countries have banned or strictly regulate germline editing in humans, though research continues in controlled settings for therapeutic purposes.

Detailed Explanation:

Answer: Option 4 — prevention of mitochondrial diseases in offspring

Pronuclear transfer is a mitochondrial replacement therapy technique used to prevent the transmission of mitochondrial diseases from mother to child. The technique involves transferring the pronuclei (nuclei from both egg and sperm before fusion) from a fertilized egg with defective mitochondria into a donor egg with healthy mitochondria but whose own pronuclei have been removed. This allows the child to inherit nuclear DNA from the biological parents while receiving healthy mitochondrial DNA from the donor, thereby preventing mitochondrial diseases.

📝 Short Notes: Mitochondrial Replacement Therapy

• Mitochondria: Cellular organelles with their own DNA (mtDNA) separate from nuclear DNA; mutations in mtDNA cause inherited mitochondrial diseases affecting muscles, nerves, brain, and other organs.
• Pronuclear Transfer (PNT): One of two main mitochondrial replacement techniques; involves transferring pronuclei from fertilized egg to donor egg with healthy mitochondria.
• Maternal Spindle Transfer (MST): Alternative technique performed before fertilization; nuclear DNA from mother's egg transferred to donor egg with healthy mitochondria.
• Three-Parent Baby: Resulting child has nuclear DNA from biological parents and mitochondrial DNA from donor (contributes <0.1% of total DNA).
• Ethical and Legal Status: First approved in UK (2015); performed in limited countries; raises ethical debates about genetic modification and germline editing.
• Applications: Prevents severe mitochondrial diseases like Leigh syndrome, MELAS, and Kearns-Sayre syndrome from being passed to offspring.

Detailed Explanation:

Answer: Option 3 — 1 and 3 only

This question tests the fundamental structural differences between plant and animal cells. Statement 2 is incorrect because both plant and animal cells possess a plasma membrane, which is a universal feature of all cells.

✅ Statement 1 – Correct: Plant cells have rigid cellulose cell walls for structural support and protection, while animal cells lack cell walls and only have a flexible plasma membrane.

❌ Statement 2 – Incorrect: Both plant and animal cells have plasma membranes (cell membranes); this is a fundamental feature present in all living cells, controlling the movement of substances in and out of the cell.

✅ Statement 3 – Correct: Mature plant cells typically contain one large central vacuole for storage of water, nutrients, and waste, whereas animal cells have multiple small vacuoles that are less prominent.

📝 Short Notes: Plant vs Animal Cells

Detailed Explanation:

Answer: Option 1 — Functional chromosomes can be created by joining segments of DNA taken from cells of different species.

This statement is incorrect because creating fully functional chromosomes by simply joining DNA segments from different species is not currently feasible. Chromosomes are highly complex structures requiring species-specific regulatory elements, centromeres, telomeres, and structural proteins that cannot be arbitrarily combined from different organisms to create functional units.

✅ Statement 1 – Incorrect: While synthetic chromosomes and chimeric DNA constructs exist, functional chromosomes cannot be simply created by joining segments from different species due to complex species-specific regulatory requirements.
✅ Statement 2 – Correct: Synthetic biology enables the chemical synthesis of artificial functional DNA sequences in laboratories, including synthetic genes and even entire viral genomes.
✅ Statement 3 – Correct: Polymerase Chain Reaction (PCR) is a standard technique that amplifies DNA segments outside living cells in vitro.
✅ Statement 4 – Correct: Cell culture and tissue culture techniques routinely enable plant and animal cells to divide and grow in laboratory petri dishes using nutrient media.

📝 Short Notes: DNA Technology & Genetic Engineering

• Synthetic DNA: Artificial DNA sequences can be chemically synthesized in laboratories for various applications including gene therapy and research.
• PCR (Polymerase Chain Reaction): A revolutionary technique developed by Kary Mullis that amplifies specific DNA segments millions of times outside living cells.
• Cell Culture: Technique of growing cells in controlled artificial conditions outside their natural environment, fundamental to biotechnology and medical research.
• Chromosomes: Complex structures consisting of DNA wrapped around histone proteins, containing centromeres, telomeres, and species-specific regulatory elements.
• Chimeric DNA: DNA constructs containing sequences from different sources, commonly used in genetic engineering, but different from functional chromosomes.
• Synthetic Biology: The field has achieved milestones like creating synthetic bacterial genomes (Mycoplasma mycoides, 2010) but functional multi-species chromosomes remain beyond current capability.

Detailed Explanation:

Answer: Option 1 — 1, 2 and 4

RNA interference (RNAi) is a biological process where RNA molecules inhibit gene expression by neutralizing targeted mRNA molecules. This technology has gained popularity for its applications in gene silencing therapies, cancer treatment, and developing disease-resistant crops.

✅ Statement 1 – Correct: RNAi technology is extensively used in developing gene silencing therapies by targeting and reducing specific gene expressions to treat various diseases.
✅ Statement 2 – Correct: RNAi-based therapies are being actively researched and developed for cancer treatment by silencing genes responsible for tumor growth and proliferation.
❌ Statement 3 – Incorrect: RNAi is not used for hormone replacement therapies; it works by silencing genes rather than introducing hormones into the body.
✅ Statement 4 – Correct: RNAi technology is successfully applied in agriculture to produce crop plants resistant to viral pathogens by targeting and degrading viral RNA.

📝 Short Notes: RNA Interference (RNAi) Technology

• Definition: RNAi is a natural cellular process where double-stranded RNA molecules trigger the degradation of specific mRNA, thereby silencing gene expression.
• Discovery: First discovered in the 1990s by Andrew Fire and Craig Mello, who won the Nobel Prize in 2006 for their work.
• Mechanism: Small interfering RNAs (siRNAs) or micro RNAs (miRNAs) bind to complementary mRNA sequences, leading to their degradation or translational repression.
• Medical Applications: Used in treating genetic disorders, viral infections, and cancer by silencing disease-causing genes; several RNAi-based drugs are in clinical trials or approved.
• Agricultural Applications: Development of virus-resistant crops, enhanced nutritional content, and improved stress tolerance in plants.
• Limitations: Off-target effects, delivery challenges to specific tissues, and potential immune responses remain areas of ongoing research.

Detailed Explanation:

Answer: Option 1 — A molecular scissors used in targeted gene editing

Cas9 is an RNA-guided endonuclease enzyme that functions as molecular scissors, capable of cutting DNA at precise locations within a genome. It is the key component of the CRISPR-Cas9 gene editing system, which has revolutionized genetic engineering by enabling targeted modifications to DNA sequences in living organisms.

📝 Short Notes: CRISPR-Cas9 Gene Editing Technology

• CRISPR-Cas9 stands for Clustered Regularly Interspaced Short Palindromic Repeats associated with Cas9 protein.
• Mechanism: The system uses a guide RNA (gRNA) to direct the Cas9 enzyme to a specific DNA sequence, where it makes a precise cut.
• Function: After cutting, the cell's natural DNA repair mechanisms can be harnessed to add, delete, or replace genetic material at the targeted location.
• Applications: Treatment of genetic diseases, development of disease-resistant crops, creation of genetically modified organisms, and basic research in genomics.
• Advantages: More precise, efficient, and cost-effective compared to earlier gene editing technologies like zinc finger nucleases and TALENs.
• Nobel Prize 2020: Emmanuelle Charpentier and Jennifer Doudna were awarded the Nobel Prize in Chemistry for developing CRISPR-Cas9 gene editing.
• Ethical Concerns: Potential misuse in human germline editing, unintended off-target effects, and ecological impacts of genetically modified organisms.

Detailed Explanation:

Answer: Option 2 — 2 only

GM Mustard (DMH-11) is a genetically modified hybrid variety of Brassica juncea developed by Delhi University's Centre for Genetic Manipulation of Crop Plants. It has been engineered with barnase-barstar genes to enable cross-pollination and hybridization for increased yield, not for pest-resistance.

✅ Statement 1 – Incorrect: GM mustard does not contain genes for pest-resistance; it is engineered for hybridization using barnase-barstar gene system, not Bt genes from soil bacteria.
✅ Statement 2 – Correct: GM mustard contains genes (barnase, barstar, and bar genes) that facilitate cross-pollination and hybridization, enabling hybrid seed production.
✅ Statement 3 – Incorrect: GM mustard was developed by Delhi University's Centre for Genetic Manipulation of Crop Plants (CGMCP), not jointly by IARI and Punjab Agricultural University.

📝 Short Notes: GM Mustard (DMH-11)

• Full Name: Dhara Mustard Hybrid-11 (DMH-11), a genetically modified variety of Brassica juncea.
• Developed by: Centre for Genetic Manipulation of Crop Plants (CGMCP), Delhi University under Prof. Deepak Pental.
• Genetic Modification: Uses barnase-barstar gene system borrowed from soil bacterium Bacillus amyloliquefaciens for male sterility and fertility restoration.
• Purpose: Enables cross-pollination in naturally self-pollinating mustard to produce high-yielding hybrids; increases yield by 25-30%.
• Key Genes: Bar gene (herbicide tolerance), barnase gene (male sterility), barstar gene (fertility restoration).
• Not Bt Crop: Unlike Bt cotton/brinjal, GM mustard does not have pest-resistance traits; it is purely for hybrid development.
• Regulatory Status: Approved by GEAC (Genetic Engineering Appraisal Committee) in 2017 but faced public and legal challenges.

Detailed Explanation:

Answer: Option 3 — Reproductive cloning of animals

Somatic Cell Nuclear Transfer (SCNT) is a cloning technique where the nucleus of a somatic (body) cell from a donor organism is transferred into an enucleated egg cell (an egg whose nucleus has been removed). The reconstructed egg is then stimulated to divide and develop into an embryo, which is implanted into a surrogate mother to produce a genetically identical clone of the donor organism. This process is called reproductive cloning.

Famous example: Dolly the sheep (1996) was the first mammal successfully cloned using SCNT technology. This technology has applications in livestock breeding, conservation of endangered species, and biomedical research. However, it is not related to biolarvicides, biodegradable plastics, or producing disease-free organisms through this specific mechanism.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

✅ Statement 1 – Correct: Genome sequencing identifies specific genetic markers linked to desirable traits such as disease resistance and drought tolerance. This enables targeted breeding programs to develop improved crop varieties with enhanced resilience.

✅ Statement 2 – Correct: Traditional crop breeding takes years or even decades. Genome sequencing accelerates this process by allowing precise identification of beneficial genes, enabling marker-assisted selection and reducing the time required to develop new varieties from 10-15 years to just 3-5 years.

✅ Statement 3 – Correct: Genome sequencing helps decode the genetic interactions between host plants and pathogens. Understanding these host-pathogen relationships enables scientists to develop targeted disease management strategies and breed crops with enhanced resistance mechanisms.

All three statements correctly describe immediate applications of genome sequencing in Indian agriculture, making it a powerful tool for crop improvement and food security.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

✅ Statement 1 – Correct: Bacteriophages (phages) are viruses that infect bacteria by injecting their genetic material into bacterial cells.
✅ Statement 2 – Correct: Mycoviruses are viruses that specifically infect fungi, often causing latent infections without visible symptoms.
✅ Statement 3 – Correct: Plant viruses infect various plant species by hijacking cellular machinery, causing diseases like mosaic patterns and stunted growth.

Detailed Explanation:

The transcriptome refers to the complete set of RNA transcripts (especially mRNA molecules) produced by the genome of an organism under specific circumstances or in a specific cell.

Unlike the static genome, the transcriptome is dynamic and reflects which genes are actively being expressed at any given time, making it crucial for understanding gene regulation, cellular functions, and responses to environmental stimuli.

Detailed Explanation:

Genetic Engineering Appraisal Committee (GEAC) is constituted under the Environment Protection Act, 1986 through the Rules for Manufacture, Use, Import, Export and Storage of Hazardous Microorganisms/Genetically Engineered Organisms or Cells, 1989.

GEAC functions as the apex body in the Ministry of Environment, Forest and Climate Change for appraisal of activities involving release of genetically engineered organisms and products into the environment, including experimental field trials.

Detailed Explanation:

❌ Statement 1 – Incorrect: Budding and grafting are traditional vegetative propagation techniques that multiply plants asexually without altering DNA; no recombinant DNA technology is used, so they do not create transgenic crops.

✅ Statement 2 – Correct: Cytoplasmic male sterility (CMS) can be manipulated through genetic engineering to introduce or transfer sterility genes into crops, creating transgenic lines for hybrid seed production.

✅ Statement 3 – Correct: Gene silencing (RNA interference/RNAi) uses engineered genetic constructs to suppress specific gene expression in plants, making it a key technique for developing transgenic crops with desired traits.

Detailed Explanation:

Photosynthesis converts light energy (free energy) from the sun into chemical energy (potential energy) and stores it in the bonds of glucose molecules.

The process uses carbon dioxide and water as raw materials and releases oxygen as a byproduct, while the stored energy in glucose can later be used by plants and other organisms.

Detailed Explanation:

✅ Statement 1 – Correct: Vegetative propagation is an asexual reproduction method where new plants grow from vegetative parts (roots, stems, leaves) without gamete fusion, producing genetically identical offspring—a clonal population.

❌ Statement 2 – Incorrect: Vegetative propagation does not eliminate viruses; instead, it propagates them. If the parent plant is virus-infected, the pathogen transmits to offspring through infected tissues.

✅ Statement 3 – Correct: Unlike sexual reproduction dependent on seasonal flowering cycles, vegetative propagation can be practiced year-round as it relies on mature vegetative organs available regardless of reproductive phase.