UPSC Prelims 2020 Science and Technology questions: topic-wise weightage
UPSC Prelims 2020 asked 13 science and technology questions in GS Paper I, spread over 3 topics. See the science and technology weightage for 2020 below, then attempt each question with the official answer and an explanation.
Science and Technology 2020: questions by topic
- Biology, health and biotechnology4
- Space technology6
- Physics and chemistry in daily life; energy and nuclear technology3
Counted from the 13 questions on this page, tagged by topic in the Battle IAS PYQ bank.
Seeing 13 Science and Technology questions spread over 3 topics can feel overwhelming. That's exactly why the Battle IAS PYQ Book maps every question topic by topic, so you know what to study first. Download free sample
Biology, health and biotechnology 4
In the context of recent advances in human reproductive technology, “Pronuclear Transfer” is used for
Answer (d) & explanation
Pronuclear transfer prevents mitochondrial diseases (d). Mitochondria have their own small set of DNA, passed on only from the mother. Faults in it cause serious diseases of the muscles, brain and heart. In pronuclear transfer, the egg of the mother is fertilised by the father's sperm. The two pronuclei, holding the parents' main DNA, are moved into a donor egg that has healthy mitochondria and whose own nuclei have been removed. The child gets the parents' genes but healthy mitochondria, hence the term "three-parent babies". It is not normal IVF (a), editing of sperm-making cells (b), or turning stem cells into embryos (c).
The UK legalised the method in 2015. Notice that in 2025, UK doctors reported eight babies born using it.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Genetic changes can be introduced in the cells that produce eggs or sperms of a prospective parent.
- 2. A person’s genome can be edited before birth at the early embryonic stage.
- 3. Human induced pluripotent stem cells can be injected into the embryo of a pig.
Which of the statements given above is/are correct ?
Answer (d) & explanation
All three statements are correct (d). Gene-editing tools such as CRISPR-Cas9 can change the DNA of germline cells, the cells that make eggs or sperm (1). Such changes would pass to future generations. A person's genome can be edited at the early embryo stage (2), as in the 2018 case of the Chinese scientist He Jiankui, who made the first gene-edited babies and was jailed. Human induced pluripotent stem (iPS) cells, made by reprogramming adult cells, have been injected into pig embryos to make human–pig chimeras (3), for research into growing human organs.
These are all technically possible but ethically debated. Notice the newer step: pig kidneys and hearts, genetically edited, were transplanted into living humans in the USA (2022–25).
Answer as per the official UPSC answer key.
What is the importance of using Pneumococcal Conjugate Vaccines in India ?
- 1. These vaccines are effective against pneumonia as well as meningitis and sepsis.
- 2. Dependence on antibiotics that are not effective against drug-resistant bacteria can be reduced.
- 3. These vaccines have no side effects and cause no allergic reactions.
Select the correct answer using the code given below :
Answer (b) & explanation
Statements 1 and 2 are correct (b). Pneumococcal Conjugate Vaccine (PCV) protects against Streptococcus pneumoniae, a bacterium that causes pneumonia, meningitis and sepsis (1). Pneumonia is a leading killer of young children in India. Statement 2 is right because fewer infections mean less antibiotic use, which slows the spread of drug-resistant bacteria. Statement 3 is wrong because, like every vaccine, PCV can cause side effects such as fever or swelling, and rare allergic reactions.
PCV was added to the Universal Immunisation Programme in 2017 and expanded across India in 2021. Notice India's own PCV, Pneumosil, made by the Serum Institute and approved in 2020. The U-WIN portal (2024) now records every vaccination digitally.
Answer as per the official UPSC answer key.
Which of the following statements are correct regarding the general difference between plant and animal cells?
- 1. Plant cells have cellulose cell walls whilst animal cells do not.
- 2. Plant cells do not have plasma membrane unlike animal cells which do.
- 3. Mature plant cell has one large vacuole whilst animal cell has many small vacuoles.
Select the correct answer using the code given below :
Answer (c) & explanation
Statements 1 and 3 are correct (c). Statement 1 is right because plant cells have a rigid cell wall made of cellulose, outside the cell membrane, which gives them shape and support. Animal cells have no cell wall. Statement 3 is right because a mature plant cell usually has one large central vacuole, filled with cell sap, which keeps the cell firm (turgid). Animal cells have only small, temporary vacuoles, or none. Statement 2 is wrong because both plant and animal cells have a plasma membrane. In plants it lies just inside the cell wall and controls what enters and leaves.
Other differences: plant cells have chloroplasts for photosynthesis, while animal cells have centrioles. Notice that fungi have walls of chitin, not cellulose.
Answer as per the official UPSC answer key.
Space technology 6
With the present state of development, Artificial Intelligence can effectively do which of the following ?
- 1. Bring down electricity consumption in industrial units
- 2. Create meaningful short stories and songs
- 3. Disease diagnosis
- 4. Text-to-Speech Conversion
- 5. Wireless transmission of electrical energy
Select the correct answer using the code given below :
Answer (b) & explanation
AI could do tasks 1, 3 and 4 in UPSC's 2020 key (b). By 2020, AI was already proven at cutting electricity use in industry (1), for example Google's DeepMind cutting data centre cooling energy by about 40%. It could help diagnose diseases (3) from X-rays, scans and eye images. It was widely used for text-to-speech (4). Statement 5 is wrong because wireless power transfer is a matter of physics, not AI. UPSC's key also left out writing meaningful stories and songs (2).
Keep the year in mind: since ChatGPT (late 2022), generative AI can clearly write stories and songs. Notice India's moves: the IndiaAI Mission (2024, ₹10,372 crore), the AI Impact Summit in New Delhi (February 2026) and AI governance guidelines (2025).
This answer reflects 2020. A question set today might count creative writing.
Answer as per the official UPSC answer key.
With reference to Visible Light Communication (VLC) technology, which of the following statements are correct ?
- 1. VLC uses electromagnetic spectrum wavelengths 375 to 780 nm.
- 2. VLC is known as long-range optical wireless communication.
- 3. VLC can transmit large amounts of data faster than Bluetooth.
- 4. VLC has no electromagnetic interference.
Select the correct answer using the code given below :
Answer (c) & explanation
Statements 1, 3 and 4 are correct (c). Visible Light Communication (VLC), also called Li-Fi, sends data by switching LED lights on and off very fast, too fast for the eye to notice. Statement 1 is right because it uses visible light, about 375–780 nm. Statement 3 is right because it can carry large amounts of data faster than Bluetooth, even faster than Wi-Fi in labs. Statement 4 is right because light causes no radio-frequency interference, so it suits hospitals, aircraft and mines. Statement 2 is wrong because light cannot pass through walls, which makes VLC a short-range technology.
Harald Haas coined the term "Li-Fi" in 2011. Notice that the IEEE 802.11bb standard (2023) brought Li-Fi into the Wi-Fi family.
Answer as per the official UPSC answer key.
With reference to “Blockchain Technology”, consider the following statements :
- 1. It is a public ledger that everyone can inspect, but which no single user controls.
- 2. The structure and design of blockchain is such that all the data in it are about cryptocurrency only.
- 3. Applications that depend on basic features of blockchain can be developed without anybody’s permission.
Which of the statements given above is/are correct ?
Answer (d) & explanation
Statements 1 and 3 are correct (d). A blockchain is a distributed ledger: a chain of linked, time-stamped records copied across many computers. Statement 1 is right because a public blockchain can be inspected by anyone, and no single user controls it; changes need agreement across the network. Statement 2 is wrong because it can record any data, such as land titles, supply chains, medical records, voting or certificates, not just cryptocurrency. Statement 3 is right because open, permissionless chains let anyone build applications, such as smart contracts, without asking permission.
Notice India's uses: land records pilots, Vishvasya, the national blockchain framework (2024), and the RBI's e-rupee (CBDC). India taxes crypto gains at 30% but has not banned crypto.
Answer as per the official UPSC answer key.
Consider the following activities :
- 1. Spraying pesticides on a crop field
- 2. Inspecting the craters of active volcanoes
- 3. Collecting breath samples from spouting whales for DNA analysis
At the present level of technology, which of the above activities can be successfully carried out by using drones ?
Answer (d) & explanation
Drones can do all three (d). Drones are used to spray pesticides and fertilisers on crops (1), saving time and reducing farmers' exposure to chemicals. India promotes Kisan drones and the Namo Drone Didi scheme (2023), which gives drones to women's SHGs. Drones fly over active volcanoes to inspect craters and sample gases (2), where it is too dangerous for people. In the SnotBot project, drones collect breath samples from spouting whales (3) for DNA, hormone and health studies, without disturbing them. So any option leaving one out is wrong.
Notice India's drone policy: the liberal Drone Rules, 2021, the PLI scheme for drones, and the ban on most imported drones (2022). Drones were used widely in Operation Sindoor (2025).
Answer as per the official UPSC answer key.
“The experiment will employ a trio of spacecraft flying in formation in the shape of an equilateral triangle that has sides one million kilometres long, with lasers shining between the craft.” The experiment in question refers to
Answer (d) & explanation
The experiment is Evolved LISA (d). The Laser Interferometer Space Antenna, in its evolved form (eLISA), plans three spacecraft flying in an equilateral triangle millions of kilometres on a side, with lasers shining between them. Tiny changes in the distance between them will reveal gravitational waves from sources such as merging giant black holes. LISA Pathfinder (c), launched in 2015, was a single craft that only tested the technology. Voyager-2 (a) is exploring interstellar space. New Horizons (b) flew past Pluto in 2015.
The mission, now just called LISA, was approved by the ESA in January 2024, with launch planned around 2035 and arms of about 2.5 million km. Notice its ground-based cousins: LIGO, Virgo, KAGRA and LIGO-India.
Pathfinder was a test of the technology using one spacecraft. The three-spacecraft triangle is the full mission.
Answer as per the official UPSC answer key.
In India, the term “Public Key Infrastructure” is used in the context of
Answer (a) & explanation
PKI refers to digital security infrastructure (a). Public Key Infrastructure is the system of encryption keys, digital certificates and certifying authorities that makes digital signatures and secure online transactions possible. Each user has a public key, which anyone can see, and a private key, kept secret. A certifying authority vouches that a public key belongs to a particular person. In India, the Controller of Certifying Authorities, under the IT Act, 2000, oversees PKI and runs the Root Certifying Authority of India. It has nothing to do with food (b), health and education (c), or transport (d).
Notice the everyday uses: Aadhaar eSign, income tax filing with digital signatures, e-tendering, and the HTTPS padlock on websites.
Answer as per the official UPSC answer key.
Physics and chemistry in daily life; energy and nuclear technology 3
With reference to carbon nanotubes, consider the following statements :
- 1. They can be used as carriers of drugs and antigens in the human body.
- 2. They can be made into artificial blood capillaries for an injured part of human body.
- 3. They can be used in biochemical sensors.
- 4. Carbon nanotubes are biodegradable.
Which of the statements given above are correct ?
Answer (c) & explanation
Statements 1, 3 and 4 are correct (c). Carbon nanotubes are tiny tubes of carbon atoms, like rolled sheets of graphene. They are very strong, light and good conductors. Statement 1 is right because they are studied as carriers of drugs and antigens (for vaccines) into cells. Statement 3 is right because they are used in biochemical sensors, for example to detect glucose or disease markers. Statement 4 is right because research has shown that enzymes such as myeloperoxidase, found in white blood cells, can break them down. Statement 2 is wrong in UPSC's key, as artificial capillaries made from them are not established.
Notice the concerns: some long nanotubes behave like asbestos in the lungs. Sumio Iijima described them in 1991.
Answer as per the official UPSC answer key.
In India, why are some nuclear reactors kept under “IAEA Safeguards” while others are not ?
Answer (b) & explanation
Some reactors use imported uranium, others domestic (b). After the 2008 India–US civil nuclear deal and the Nuclear Suppliers Group waiver, India separated its civilian and military facilities. Reactors fuelled by imported uranium (from Russia, Kazakhstan, Canada and others) are placed under IAEA safeguards, so suppliers can check the fuel is not used for weapons. Reactors on domestic uranium and the strategic programme stay outside. Option (a) is wrong because thorium is not the dividing line. Options (c) and (d) are wrong because all Indian power reactors are run by state-owned firms such as NPCIL.
Notice India's three-stage nuclear programme, planned by Homi Bhabha: PHWRs, then fast breeder reactors, then thorium reactors. India is not a member of the NPT.
Answer as per the official UPSC answer key.
With reference to solar water pumps, consider the following statements :
- 1. Solar power can be used for running surface pumps and not for submersible pumps.
- 2. Solar power can be used for running centrifugal pumps and not the ones with piston.
Which of the statements given above is/are correct ?
Answer (d) & explanation
Neither statement is correct (d). Statement 1 is wrong: solar panels can run both surface pumps, which lift water from ponds and canals, and submersible pumps, which sit inside a borewell. Statement 2 is wrong: solar power can run both centrifugal pumps and positive-displacement pumps, such as piston pumps. Each statement wrongly rules out one type; the pump type depends on the water depth and flow needed, not on the power source.
Notice PM-KUSUM (2019), which subsidises standalone solar pumps, solarisation of grid-connected pumps, and small solar plants on farmland. Solar pumps cut diesel use and power subsidies, but critics warn that free daytime power can lead to over-extraction of groundwater.
Answer as per the official UPSC answer key.
All years by topic
Every question from 2011 to 2026, grouped by syllabus topic, with year-wise trends.