Gel electrophoresis separates DNA fragments primarily by what property?

Gel electrophoresis separates DNA fragments primarily by what property?

• A. Size
• B. Sequence
• C. Charge
• D. Hydrophobicity

Answer: (D)

Gel electrophoresis separates DNA fragments primarily by size. DNA carries a uniform negative charge along its phosphate backbone, so when an electric field is applied, all fragments migrate toward the positive electrode. The gel itself is a porous network (like agarose or polyacrylamide). Smaller fragments fit through the pores more easily and move faster, while larger ones move more slowly, creating a size-based separation. Because the charge per base pair is roughly the same, the charge-to-mass ratio is similar across fragments, making size the dominant factor in how far a fragment travels. Hydrophobicity isn’t a driver in this setup, and sequence differences don’t typically change mobility under standard conditions. This is why DNA ladders with known fragment sizes are used to estimate the sizes of unknown fragments.

Gel electrophoresis separates DNA fragments primarily by size. DNA carries a uniform negative charge along its phosphate backbone, so when an electric field is applied, all fragments migrate toward the positive electrode. The gel itself is a porous network (like agarose or polyacrylamide). Smaller fragments fit through the pores more easily and move faster, while larger ones move more slowly, creating a size-based separation. Because the charge per base pair is roughly the same, the charge-to-mass ratio is similar across fragments, making size the dominant factor in how far a fragment travels. Hydrophobicity isn’t a driver in this setup, and sequence differences don’t typically change mobility under standard conditions. This is why DNA ladders with known fragment sizes are used to estimate the sizes of unknown fragments.