In gel electrophoresis, which property primarily determines the separation of DNA fragments?

In gel electrophoresis, which property primarily determines the separation of DNA fragments?

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

Answer: (C)

The separation in gel electrophoresis is governed by fragment length because the gel matrix acts as a sieve. All double-stranded DNA carries a similar negative charge per base pair, so the electric driving force is roughly the same for fragments of different lengths; what changes their speed is how much the gel impedes their movement. Smaller fragments can snake through the pores more easily and thus migrate faster, while larger fragments experience more resistance and move slower, creating a size-based separation. Sequence doesn’t determine how fast a fragment migrates under standard conditions, and while mass relates to size, it’s the length that primarily drives the separation.

The separation in gel electrophoresis is governed by fragment length because the gel matrix acts as a sieve. All double-stranded DNA carries a similar negative charge per base pair, so the electric driving force is roughly the same for fragments of different lengths; what changes their speed is how much the gel impedes their movement. Smaller fragments can snake through the pores more easily and thus migrate faster, while larger fragments experience more resistance and move slower, creating a size-based separation. Sequence doesn’t determine how fast a fragment migrates under standard conditions, and while mass relates to size, it’s the length that primarily drives the separation.