Which technique analyzes DNA fragment lengths after restriction enzyme digestion?

• A. PCR
• B. RAPD
• C. RFLP
• D. Sanger Sequencing

Answer: (C)

RFLP analyzes DNA fragment lengths after restriction enzyme digestion by focusing on how sequence differences alter where a DNA molecule is cut. When a genome is treated with restriction enzymes, the DNA is cut at specific short sequences, producing fragments whose sizes depend on where those sites occur. If an individual has a polymorphism that changes a restriction site or the distance between sites, the lengths of the resulting fragments differ. Running these fragments on a gel reveals a pattern of bands whose presence or absence and sizes reflect the underlying genetic variation. This approach relies on comparing fragment-length patterns across samples to detect polymorphisms.

Other techniques don’t center on this kind of fragment-length analysis after digestion: PCR amplifies a targeted region to copy it, rather than assessing the entire digest pattern; RAPD uses random primers to generate fingerprint fragments without relying on known restriction sites; Sanger sequencing determines the exact nucleotide sequence rather than comparing fragment lengths after digestion.