Biotechnology & genetics

Answer: (a) Controlling the viral diseases spread by mosquitoes

The Wolbachia method is used to control viral diseases spread by mosquitoes, mainly dengue. Wolbachia is a bacterium that lives naturally in many insects; when it is introduced into Aedes aegypti mosquitoes, they transmit dengue virus much less.

• ✓ (a) Wolbachia has been transferred into Aedes aegypti mosquitoes and reduces their transmission of dengue virus. WHO's Vector Control Advisory Group has assessed the approach and confirmed its public health value for dengue control.
• ✗ (b) Turning crop residue into packing material is a materials process and has nothing to do with a bacterium living inside insects.
• ✗ (d) Biochar comes from heating biomass in a thermochemical process such as pyrolysis. It is not a mosquito-control method.

Remember · Wolbachia is an insect-dwelling bacterium. Released in Aedes aegypti mosquitoes, it cuts dengue transmission, so it is a mosquito-borne disease control method.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) Collecting DNA samples from air in a habitat at one go

Aerial metagenomics means collecting DNA from the air in a habitat and sequencing it all together to see which organisms are present. Metagenomics studies the combined genetic material of many organisms in one bulk sample, and here the sample is air.

• ✓ (a) Air carries tiny particles (bioaerosols) shed by microbes, plants and animals. Sampling that air and sequencing the DNA in it at one go reveals the species around, without catching or disturbing any animal.
• ✗ (b) This describes genetic study of birds only. Metagenomics covers a whole mixed community of organisms in one sample, not one group such as avian species.
• ✗ (d) Drones collecting physical plant and animal samples from land and water are a sampling method, not a study of DNA collected from air.

Remember · Metagenomics reads the DNA of a whole community from one bulk sample. In aerial metagenomics that sample is air, giving a snapshot of the species around.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (a) Studying the evolutionary relationships among various species of fauna

Microsatellite DNA is used to study genetic variation between individuals and populations, which is why it helps in tracing evolutionary relationships among species. Microsatellites are short DNA stretches repeated many times, and the number of repeats varies from one organism to another.

• ✓ (a) Because repeat numbers in microsatellites differ so much between individuals and populations, they work as genetic markers. Comparing them shows how closely related organisms or populations are.
• ✗ (b) Turning stem cells into different tissues is done with growth signals and culture conditions. It does not use microsatellite DNA.
• ✗ (d) Drug trials in a population test how well a medicine works. Microsatellites do not assess drug efficacy.

Remember · Microsatellites are short repeated DNA stretches whose repeat number varies between individuals. They serve as genetic markers, for DNA fingerprinting and for studying relationships and diversity.

📘 Read it in NCERT: Class 12 Biology, Ch 5 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error