Why does DNA move through the gel during gel electrophoresis?

• A. Because DNA is hydrophobic and moves away from water in the gel.
• B. Because DNA is neutral and moves randomly through the gel.
• C. Because DNA is positively charged and moves towards the negative electrode.
• D. Because DNA is negatively charged and moves towards the positive electrode.

Answer: (D)

Verified step by step guidance

1. Understand the basic principle of gel electrophoresis: it is a technique used to separate DNA fragments based on their size and charge.
2. Recognize that DNA molecules have a negative charge due to their phosphate backbone. This is crucial for understanding their movement in an electric field.
3. In gel electrophoresis, an electric field is applied across the gel. The negatively charged DNA molecules are attracted to the positive electrode (anode) and move through the gel towards it.
4. The gel acts as a sieve, allowing smaller DNA fragments to move faster and further than larger ones, which is why DNA fragments are separated by size during electrophoresis.
5. Remember that the movement of DNA through the gel is not random; it is directed by the electric field and influenced by the size of the DNA fragments.