Science and Technology questions in UPSC Prelims often decide who clears the cutoff and who misses it by a whisker. Over the last decade, I have noticed that UPSC repeats certain themes and conceptual patterns in this section — and understanding those patterns gives you a genuine edge on exam day.
This piece walks you through fifteen high-value previous year questions, each solved with clear reasoning and linked back to the concept UPSC was actually testing. Whether you are starting your preparation fresh in 2026 or revising for your second attempt, these solved PYQs will sharpen your understanding significantly.
Where This Topic Sits in the UPSC Syllabus
Science and Technology is part of the General Studies paper in both Prelims and Mains. The syllabus line reads: “General issues on Environmental Ecology, Bio-diversity and Climate Change” and “Achievements of Indians in Science & Technology; Indigenization of Technology and developing new technology.” For Mains, it falls under GS-III with a broader scope covering awareness in IT, space, computers, robotics, nano-technology, and biotechnology.
| Exam Stage | Paper | Syllabus Section |
|---|---|---|
| Prelims | General Studies Paper I | Science and Technology — developments and applications |
| Mains | GS-III | Awareness in S&T, Space, IT, Biotech, IPR issues |
On average, 8 to 14 questions in Prelims come directly or indirectly from Science and Technology. The weight has been increasing since 2018, making this section impossible to ignore.
Biotechnology and Health Sciences — The Favourite Zone
UPSC loves biotechnology. Questions on DNA technology, CRISPR gene editing, monoclonal antibodies, and vaccine platforms have appeared repeatedly. In 2022, a question asked about the difference between mRNA vaccines and traditional vaccines. The key concept tested was whether candidates understood that mRNA vaccines do not use a weakened virus — they use genetic instructions to trigger an immune response.
Another recurring theme is genetically modified organisms. UPSC has asked about Bt Cotton, Bt Brinjal, and Golden Rice multiple times. The trick here is knowing which GM crops are approved for commercial cultivation in India. As of 2026, only Bt Cotton is commercially approved. Bt Brinjal remains unapproved despite clearing biosafety tests.
A 2019 question tested knowledge about DNA profiling and its use in criminal investigations. The concept behind it was the uniqueness of Short Tandem Repeats (STRs) in human DNA. If you understand that no two individuals (except identical twins) share the same STR pattern, you can solve any question UPSC frames around forensic science.
Space Technology — ISRO and Beyond
ISRO-related questions are almost guaranteed every year. UPSC has asked about launch vehicles (PSLV vs GSLV), types of satellite orbits, and specific missions like Chandrayaan and Mangalyaan. A 2021 question asked which orbit is used for communication satellites. The answer is Geostationary Orbit (GEO) at approximately 36,000 km altitude, where the satellite matches Earth’s rotation and appears stationary over one point.
In 2023, a question tested understanding of the Gaganyaan mission. The concept tested was whether candidates knew it is India’s first human spaceflight programme, not just another satellite launch. UPSC often frames such questions with multiple statements, asking which are correct. The strategy here is to focus on elimination — find the one statement you are sure is wrong.
Another common area is the difference between polar and equatorial orbits. PSLV typically places satellites in Sun-Synchronous Polar Orbits, useful for Earth observation. GSLV places heavier satellites in Geosynchronous Transfer Orbits. Knowing this basic distinction helps you solve at least one question every year.
Nuclear Technology and Energy
India’s three-stage nuclear programme designed by Homi Bhabha is a classic UPSC topic. The first stage uses natural uranium in Pressurised Heavy Water Reactors. The second stage uses plutonium in Fast Breeder Reactors. The third stage will use thorium, which India has in abundance. UPSC has tested this sequence at least three times in the last fifteen years.
A 2020 question asked about the fuel used in India’s Fast Breeder Reactor at Kalpakkam. The answer is a mixed oxide of uranium and plutonium. Many aspirants confuse this with thorium, which belongs to the third stage — a mistake UPSC specifically designs the question to trigger.
Information Technology and Cyber Security
With India’s push towards Digital India, questions on blockchain, artificial intelligence, and cloud computing have become frequent. A 2023 Prelims question asked about the applications of blockchain beyond cryptocurrency. The correct understanding is that blockchain is a distributed ledger technology useful in land records, supply chain management, and digital identity verification — not just Bitcoin.
Cyber security questions often test awareness of terms like ransomware, phishing, and zero-day vulnerabilities. UPSC does not ask deep technical questions here. It tests whether you understand the basic meaning and real-world implications of these terms. A simple practice — read the Technology section of any major newspaper daily for three months — covers this area well.
Defence Technology and Missiles
India’s missile programme under DRDO is another reliable source of questions. Know the classification: Prithvi (short-range, surface-to-surface), Agni series (medium to intercontinental range), BrahMos (supersonic cruise missile, joint venture with Russia), and Akash (surface-to-air). A 2018 question specifically tested whether BrahMos is a cruise missile or a ballistic missile. The answer is cruise — it flies at low altitude and follows a guided path, unlike ballistic missiles that follow a parabolic trajectory.
Emerging Technologies — AI, Quantum Computing, Nano-tech
UPSC has started testing awareness of frontier technologies. Quantum computing questions test whether you understand the concept of qubits — which can exist in multiple states simultaneously, unlike classical bits that are either 0 or 1. This property is called superposition.
Nanotechnology questions are usually straightforward. Know that nanotechnology deals with materials at the scale of 1 to 100 nanometres, and its applications span medicine (targeted drug delivery), textiles (stain-resistant fabrics), and electronics (smaller, faster chips). A 2017 question combined nanotechnology with environmental science, asking about its use in water purification — a cross-topic pattern UPSC favours.
How to Approach Science and Technology for Prelims 2026
From my experience teaching aspirants, I recommend a three-source strategy. First, read the Science and Technology section from your standard reference book — Shankar IAS or TMH Science is sufficient. Second, follow monthly current affairs compilations for new missions, policies, and technologies. Third, solve every PYQ from 2011 onwards — you will see patterns emerge clearly.
Do not try to study Science and Technology like an engineering textbook. UPSC tests awareness and application, not technical depth. If you understand the basic principle behind a technology and know its Indian context, you can answer most questions correctly.
Key Points to Remember for UPSC
- Only Bt Cotton is commercially approved for cultivation in India — no other GM crop has approval as of 2026.
- India’s three-stage nuclear programme moves from uranium to plutonium to thorium — sequence matters in Prelims.
- PSLV serves polar orbits for remote sensing; GSLV serves geosynchronous orbits for communication satellites.
- Blockchain is a distributed ledger technology with applications far beyond cryptocurrency — land records, supply chain, identity.
- BrahMos is a supersonic cruise missile, not a ballistic missile — this distinction has been tested directly.
- mRNA vaccines use genetic instructions, not weakened pathogens — a concept tested in post-COVID Prelims papers.
- Quantum computing relies on superposition and entanglement — understand these two terms at a basic level.
- UPSC favours cross-topic questions combining S&T with environment, governance, or ethics — prepare accordingly.
Solving PYQs is not just about finding the right answer — it trains your mind to think the way UPSC frames questions. Go through each of these themes, revise the underlying concepts, and attempt at least two full mock tests focused on Science and Technology before your 2026 Prelims. Consistent, focused practice in this section can realistically add 10 to 15 marks to your score.