Which method is most commonly used to separate genomic DNA fragments by size?

• A. Agarose gel electrophoresis
• B. Polymerase chain reaction (PCR)
• C. Sanger DNA sequencing
• D. Southern blot hybridization

Answer: (A)

Verified step by step guidance

1. Understand that the question asks about a method used to separate genomic DNA fragments based on their size.
2. Recall that agarose gel electrophoresis is a technique where DNA fragments are placed in a gel matrix and an electric current is applied, causing fragments to migrate through the gel.
3. Recognize that smaller DNA fragments move faster and travel farther through the agarose gel compared to larger fragments, allowing separation by size.
4. Compare this with other options: PCR amplifies DNA but does not separate fragments by size; Sanger sequencing determines the nucleotide sequence; Southern blotting involves transfer and hybridization but requires prior separation of DNA fragments.
5. Conclude that agarose gel electrophoresis is the most commonly used method for separating genomic DNA fragments by size.