Describe the basic principle of DNA gel electrophoresis.

Describe the basic principle of DNA gel electrophoresis.

• A. DNA moves toward the negative electrode regardless of size
• B. DNA fragments migrate through a gel matrix under an electric field; smaller fragments move faster toward the positive electrode
• C. Gels cannot separate fragments by size
• D. The gel matrix acts as a nutrient source

Answer: (B)

DNA gel electrophoresis separates DNA fragments by size using an electric field. DNA carries many negative charges on its backbone, so when voltage is applied, fragments migrate toward the positive electrode. The gel’s porous matrix acts as a sieve: smaller fragments navigate the pores with less resistance and move faster, while larger fragments move more slowly. This size-dependent movement creates distinct bands at different distances from the origin, which you can compare to a ladder of known sizes to estimate fragment lengths. In short, movement is driven by charge toward the positive end, and separation arises because smaller pieces travel farther through the gel than larger ones.

DNA gel electrophoresis separates DNA fragments by size using an electric field. DNA carries many negative charges on its backbone, so when voltage is applied, fragments migrate toward the positive electrode. The gel’s porous matrix acts as a sieve: smaller fragments navigate the pores with less resistance and move faster, while larger fragments move more slowly. This size-dependent movement creates distinct bands at different distances from the origin, which you can compare to a ladder of known sizes to estimate fragment lengths. In short, movement is driven by charge toward the positive end, and separation arises because smaller pieces travel farther through the gel than larger ones.