Since DNA has a negative charge, which technique is commonly used to separate DNA fragments by size?

• A. Chromatography
• B. PCR amplification
• C. Gel electrophoresis
• D. Centrifugation

Answer: (C)

Verified step by step guidance

1. Understand that DNA molecules carry a negative charge due to their phosphate backbone.
2. Recognize that to separate DNA fragments by size, a technique must exploit this charge property to move DNA through a medium.
3. Recall that gel electrophoresis is a method where an electric field is applied to a gel matrix, causing negatively charged DNA fragments to migrate towards the positive electrode.
4. Know that smaller DNA fragments move faster and travel farther through the gel pores than larger fragments, allowing size-based separation.
5. Conclude that among the options, gel electrophoresis is the technique commonly used to separate DNA fragments by size because it uses the negative charge of DNA and a gel matrix to achieve this separation.