'Microsatellite DNA' is used in the case of which one of the following?

(a) Studying the evolutionary relationships among various species of fauna ✓ UPSC's answer
(b) Stimulating 'stem cells' to transform into diverse functional tissues
(c) Promoting clonal propagation of horticultural plants
(d) Assessing the efficacy of drugs by conducting series of drug trials in a population

Why the answer is (a)

• Microsatellites (short tandem repeats) are stretches of DNA in which a short motif of 1–6 bases is repeated many times; the number of repeats varies greatly between individuals and populations.

• Because they mutate rapidly and are inherited, microsatellite markers are used to study genetic diversity, population structure and evolutionary relationships among species and populations, as well as in parentage tests and forensic DNA fingerprinting — option (a).

• They are widely used in wildlife genetics, e.g. to estimate tiger populations from scat.

• They have no role in stem-cell differentiation, clonal propagation of plants or drug trials.

• Hence option (a).

Why the other options are wrong

(b) Stimulating 'stem cells' to transform into diverse functional tissues: Stem-cell differentiation is controlled by growth factors, not microsatellite DNA.
(c) Promoting clonal propagation of horticultural plants: Clonal propagation uses tissue culture, not microsatellites.
(d) Assessing the efficacy of drugs by conducting series of drug trials in a population: Drug trials assess efficacy clinically, not with microsatellite markers.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2023, held on 28 May 2023. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.