Question

Which of the following molecular marker techniques is the best for studying genome-wide genetic variation in crop plants ?

• A. RFLP
• B. RAPD
• C. AFLP
• D. SNP

Hint:

To remember marker properties:
- RFLP $\rightarrow$ Co-dominant, low throughput, non-PCR.
- RAPD $\rightarrow$ Dominant, poor reproducibility, random primers.
- AFLP $\rightarrow$ Dominant, highly multiplexed, restriction-based.
- SNP $\rightarrow$ Co-dominant, extremely high-throughput, sequence-based (ideal for genome-wide studies).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Molecular markers are identifiable DNA sequences that can be used to track inheritance and analyze genetic variation within and between species.
Choosing the best marker system depends on factors such as genome abundance, reproducibility, cost, and high-throughput automation capacity.

Step 2: Detailed Explanation:
Let us analyze the characteristics of the listed molecular marker systems:
1. RFLP (Restriction Fragment Length Polymorphism):
This is a co-dominant, hybridization-based marker system.
While highly reproducible, it is slow, requires large quantities of high-quality DNA, and is not suitable for high-throughput genome-wide analysis.
Thus, Option (A) is incorrect.
2. RAPD (Random Amplified Polymorphic DNA):
This is a PCR-based dominant marker system that uses short, arbitrary primers.
It is highly sensitive to reaction conditions, making it poorly reproducible and unsuitable for large-scale genetic studies.
Thus, Option (B) is incorrect.
3. AFLP (Amplified Fragment Length Polymorphism):
This is a PCR-based marker system that combines restriction digestion with selective amplification.
While highly reproducible and generating many bands, it is complex, labor-intensive, and dominant in nature.
Thus, Option (C) is incorrect.
4. SNP (Single Nucleotide Polymorphism):
SNPs represent single-base-pair differences in DNA sequences among individuals.
They are the most abundant type of genetic variation in genomes, occurring once every few hundred base pairs in most crop genomes.
Because they are single-nucleotide variations, they can be analyzed using high-throughput automation technologies like SNP microarrays (chips) and Next-Generation Sequencing (NGS).
This high abundance and automation capacity make SNPs the premier tool for genome-wide association studies (GWAS), genomic selection, and high-resolution genetic mapping.

Step 3: Final Answer:
The best molecular marker technique for studying genome-wide genetic variation is SNP.
This corresponds to Option (D).