Question

Which among the following is true for RFLP?

• A. It cannot be used as a genetic marker
• B. It refers to differences (or variations) in the DNA sequences at sites recognized by restriction enzymes
• C. Restriction enzymes are not used for digesting DNA in this process
• D. It is a PCR based marker

Hint:

• RFLP Restriction Fragment Length Polymorphism.
• Variation in DNA sequence (e.g., SNP) that creates or abolishes a restriction enzyme recognition site.
• Leads to different lengths of DNA fragments after digestion with that restriction enzyme.
• Detected by Southern blotting or PCR-RFLP.
• Used as genetic markers.

Answer 1

The Correct Option is B

RFLP (Restriction Fragment Length Polymorphism) is a type of polymorphism (variation in DNA sequence among individuals) that results in differences in the lengths of DNA fragments produced when DNA is digested with specific restriction enzymes. Mechanism:

• Restriction enzymes cut DNA at specific recognition sequences.
• If a mutation (e.g., a single nucleotide polymorphism - SNP) occurs within a restriction site, it can abolish that site, preventing the enzyme from cutting there.
• Alternatively, a mutation can create a new restriction site.
• These changes alter the lengths of the DNA fragments generated by restriction enzyme digestion.
• These different-sized fragments can be detected by techniques like Southern blotting (after gel electrophoresis) using a probe that hybridizes to the region containing the polymorphism.

RFLPs are used as genetic markers for linkage analysis, gene mapping, DNA fingerprinting, and disease diagnosis. Let's analyze the options: (a) "It cannot be used as a genetic marker": FALSE. RFLPs were one of the first widely used types of DNA-based genetic markers. (b) "It refers to differences (or variations) in the DNA sequences at sites recognized by restriction enzymes": TRUE. These sequence differences can create or abolish restriction sites, leading to fragments of different lengths. (c) "Restriction enzymes are not used for digesting DNA in this process": FALSE. The "R" in RFLP stands for Restriction. Digestion with restriction enzymes is a fundamental step. (d) "It is a PCR based marker": While PCR can be used to amplify the DNA region containing an RFLP before restriction digestion (PCR-RFLP), RFLP itself is defined by restriction enzyme digestion patterns and was originally detected by Southern blotting without PCR. PCR is not an inherent part of the definition of RFLP, though it can be incorporated into the detection method. RFLP is based on sequence variation affecting restriction sites. Therefore, option (b) is the true statement for RFLP. \[ \boxed{\text{It refers to differences (or variations) in the DNA sequences at sites recognized by restriction enzymes}} \]