Biotechnology & genetics

Answer: (d) prevention of mitochondrial diseases in offspring

Pronuclear transfer is a form of mitochondrial donation, used to stop a mother from passing a serious mitochondrial disease to her child. The nuclear DNA of her fertilised egg is moved into a donor egg that has healthy mitochondria, so the baby gets the parents' genes but the donor's healthy mitochondria.

• ✗ (a) Fertilising an egg in the lab with donor sperm is ordinary IVF. Pronuclear transfer is an extra step done on embryos, not a way of fertilising an egg.
• ✗ (b) The technique does not modify sperm-producing cells or edit genes; it swaps whole nuclear material between embryos.
• ✗ (c) It does not turn stem cells into embryos. It moves the nuclear genetic material of one embryo into another embryo whose own nucleus has been removed.
• ✓ (d) Mitochondrial donation treatment lets people with severe mitochondrial disease avoid passing it to their children. Pronuclear transfer is one of the two approved techniques, the other being maternal spindle transfer.

Remember · Pronuclear transfer = swap the nuclear DNA of an embryo into a donor embryo with healthy mitochondria, to prevent mitochondrial disease.

Question and answer: UPSC's official GS Paper I (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) 1, 3 and 4 only

Carbon nanotubes are tiny hollow tubes of rolled-up carbon sheets that are used in medicine to carry drugs and in biochemical sensors, and living systems can break them down with enzymes. Making artificial blood capillaries from them is not an established use, so statement 2 is the one that fails.

• ✓ 1. Carbon nanotubes are used as carriers, for example to deliver drugs and other payloads in the body, and are studied for bioimaging as well.
• ✗ 2. The established medical uses are bioimaging, drug delivery and biosensing. Building artificial blood capillaries for an injured body part is not one of them.
• ✓ 3. Biosensing is one of the main biomedical uses of functionalised carbon nanotubes.
• ✓ 4. Enzymes such as peroxidases can degrade carbon nanotubes, so they can be cleared from the body after delivering their payload; research is now focused on this route.

Remember · Carbon nanotubes: drug carriers and biosensors, and enzyme-degradable; not used as artificial blood capillaries.

Question and answer: UPSC's official GS Paper I (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (d) 1, 2 and 3

All three statements describe things that science can already do: edit the genes of egg- and sperm-producing cells, edit the genome of a very early embryo, and inject human stem cells into a pig embryo to make a human-pig chimera. The word 'can' asks about technical possibility, not legal permission.

• ✓ 1. Gene editing of germ-line stem cells and gametes (eggs and sperm) is possible. India's stem cell guidelines name it and restrict such work to laboratory (in vitro) studies.
• ✓ 2. Germline editing means changing genes in eggs, sperm or very early embryos, and the change is heritable. So a person's genome can be edited at the early embryonic stage.
• ✓ 3. Human induced pluripotent stem cells (iPSCs, adult cells reprogrammed to an embryo-like state) have been injected into pig embryos. Some of the human iPSCs took part in the pig embryos' development, giving a chimera.

Remember · Germline and embryo editing and human-animal chimeras are technically possible today, though India restricts them to regulated laboratory work.

Question and answer: UPSC's official GS Paper I (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error