Q55 Match the tasks given in Group I with the associated techniques conventionally used as listed in Group II

Correct answer: (B) P‑3; Q‑4; R‑1; S‑2; T‑5

Introduction

This question tests conceptual clarity about matching tasks with molecular biology techniques that are routinely used in genomics and epigenetics research. Correctly pairing each experimental goal with its conventional method is essential for CSIR NET and other life‑science competitive exams because it reflects practical understanding of how modern high‑throughput tools are applied in real laboratories.​

Step‑wise matching of Group I and Group II

P. Ploidy analysis → 3. Fluorescence in situ hybridization

• Fluorescence in situ hybridization (FISH) uses fluorescently labeled DNA probes hybridized to chromosomes to visualize and count specific chromosome regions or whole chromosomes, making it highly suitable for assessing ploidy or aneuploidy at the single‑cell level.​

• By counting fluorescent signals per nucleus, FISH allows detection of diploidy, polyploidy and chromosomal gains or losses, which is exactly what ploidy analysis requires.​

So, P‑3 is correct.

Q. Profiling DNA methylation → 4. Bisulfite sequencing

• Bisulfite sequencing involves treating DNA with sodium bisulfite, which converts unmethylated cytosines to uracils while methylated cytosines remain as cytosines; subsequent sequencing reveals methylation status at single‑base resolution.​

• Because of this base‑level discrimination, bisulfite sequencing is considered a gold‑standard technique for profiling DNA methylation patterns across genomic regions or even genome‑wide.​

Thus, Q‑4 is the correct match.

R. Identifying non‑coding RNAs → 1. RNA sequencing

• RNA sequencing (RNA‑seq) captures and sequences the entire transcriptome, enabling discovery and quantification of coding and non‑coding RNAs, including lncRNAs, miRNAs (with appropriate library prep) and other novel ncRNA species.​

• Many studies use RNA‑seq specifically to identify and characterize long non‑coding RNAs and other regulatory transcripts that are not translated into proteins.​

Therefore, R‑1 is correct.

S. Identifying SNPs → 2. Exome sequencing

• Exome sequencing selectively captures and sequences exonic regions (protein‑coding parts) of the genome at high depth, which is particularly effective for detecting single nucleotide polymorphisms (SNPs) and small variants in genes.​

• While whole‑genome sequencing can also reveal SNPs, exome sequencing is a cost‑effective standard approach when the objective is identifying SNPs associated with diseases or traits.​

Hence, S‑2 is the appropriate match.

T. Satellite DNA isolation → 5. Density‑gradient centrifugation

• Density‑gradient centrifugation separates nucleic acids based on buoyant density in gradients such as cesium chloride, allowing enrichment of specific DNA fractions like highly repetitive, AT‑ or GC‑rich satellite DNA which band at characteristic densities.​

• This classical physical separation method has long been used for isolating satellite DNA and other repetitive sequences from bulk genomic DNA preparations.​

Thus, T‑5 is correct.

Why the other options are wrong

The options given are:

• (A) P‑2; Q‑1; R‑3; S‑4; T‑5

• (B) P‑3; Q‑4; R‑1; S‑2; T‑5

• (C) P‑5; Q‑4; R‑1; S‑2; T‑3

• (D) P‑3; Q‑5; R‑1; S‑2; T‑4

Analysis:

• In option (A), P‑2 wrongly links ploidy analysis with exome sequencing, which targets coding DNA rather than chromosome number, and Q‑1 incorrectly uses RNA‑seq for DNA methylation profiling, which requires bisulfite‑based methods.​

• In option (C), P‑5 incorrectly assigns density‑gradient centrifugation to ploidy analysis (it separates by density, not chromosome count) and T‑3 wrongly uses FISH for satellite DNA isolation, even though FISH is a visualization, not a preparative isolation method.​

• In option (D), Q‑5 misuses density‑gradient centrifugation for DNA methylation profiling and T‑4 incorrectly applies bisulfite sequencing to isolate satellite DNA instead of to measure methylation.​

Only option (B) correctly pairs every task with its conventional technique, so (B) is the right answer.