Biotechnology & genetics

Answer: (c) Both 1 and 2

Both statements are correct: a recombinant vector vaccine is built by genetic engineering, and the carrier (vector) that delivers the disease-causing agent's gene into our cells is a harmless virus or bacterium.

• ✓ 1. Recombinant DNA technology lets scientists make a pathogen's antigen in bacteria or yeast, as with the hepatitis B vaccine from yeast. Recombinant vector vaccines rest on the same gene-splicing methods.
• ✓ 2. NIAID, part of the US National Institutes of Health, describes recombinant vector vaccines as those that use a harmless virus or bacterium as a vector, or carrier, to introduce genetic material into cells. Covishield is a vectored vaccine that uses a virus as the carrier.

Remember · Recombinant vector vaccine = genetic engineering plus a harmless virus or bacterium as the carrier that delivers the pathogen's gene into our cells.

📘 Read it in NCERT: Class 12 Biology, Ch 7 (practise this chapter) · Class 12 Biology, Ch 9 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (c) Both 1 and 2

Both statements are correct: mitochondrial DNA comes only from the mother's egg, and mitochondrial replacement therapy swaps the faulty mitochondria either before fertilisation (spindle transfer) or after it (pronuclear transfer).

• ✓ 1. Two techniques are used: in maternal spindle transfer the mother's nuclear genetic material is moved into a donor egg before fertilisation, and in pronuclear transfer the fertilised embryo's nuclear material is moved into a donor embryo after fertilisation. Either way the child gets healthy donor mitochondria.
• ✓ 2. Only egg cells contribute mitochondria to the embryo, so only females pass on mitochondrial DNA variants; a father's sperm does not pass them on.

Remember · Mitochondrial DNA is inherited only from the mother. Mitochondrial replacement therapy: spindle transfer (before fertilisation) or pronuclear transfer (after fertilisation).

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) developing genetically modified crop plants

Bollgard I and Bollgard II are brand names of Bt cotton technology, that is, genetically modified cotton carrying Bt genes that protect it from bollworm pests. So they belong to developing genetically modified crop plants.

• ✓ (b) Bt cotton is a genetically modified crop: a Bt toxin gene from the bacterium Bacillus thuringiensis is expressed in the plant to resist insects. In Bollgard II hybrids, both the Cry1Ac and Cry2Ab proteins are present in the transgenic plant.
• ✗ (a) Clonal propagation copies plants from cuttings or tissue culture without adding genes; Bollgard involves inserted genes.
• ✗ (c) Plant growth substances are hormones such as auxins; Bollgard is not a hormone-making technology.
• ✗ (d) Biofertilizers are living microbes added to soil, whereas Bollgard is a trait built into the cotton plant itself.

Remember · Bollgard I and Bollgard II = Bt cotton (GM cotton); Bollgard II carries two Bt proteins, Cry1Ac and Cry2Ab.

📘 Read it in NCERT: Class 12 Biology, Ch 10 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) 2 only

Statement 2 is correct: adenoviruses can cause cold-like illness, and AIDS is caused by HIV, which is a retrovirus. Statement 1 is wrong on both counts, because adenoviruses have double-stranded DNA genomes, while retroviruses carry an RNA genome.

• ✗ 1. Adenoviruses are non-enveloped viruses with double-stranded DNA, not single-stranded DNA. Retroviruses, such as HIV, have an RNA genome (later copied into DNA inside the host cell), not a double-stranded DNA genome.
• ✓ 2. Adenoviruses cause respiratory infections, including mild cold-like illness. AIDS is caused by the Human Immunodeficiency Virus (HIV), a retrovirus.

Remember · Adenovirus: double-stranded DNA, respiratory infections. Retrovirus (HIV, cause of AIDS): RNA genome.

📘 Read it in NCERT: Class 12 Biology, Ch 7 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error