During gel electrophoresis, how does $\mathrm{DNA}$ move through the gel?

• A. $\mathrm{DNA}$ moves towards the $\mathrm{negative}$ electrode due to its $\mathrm{positive}$ charge.
• B. $\mathrm{DNA}$ moves randomly due to thermal motion.
• C. $\mathrm{DNA}$ moves towards the $\mathrm{positive}$ electrode due to its $\mathrm{negative}$ charge.
• D. $\mathrm{DNA}$ remains stationary because it is $\mathrm{neutral}$.

Answer: (C)

Verified step by step guidance

1. Understand the basic principle of gel electrophoresis: it is a technique used to separate DNA fragments based on size by applying an electric field.
2. Recognize that DNA molecules are negatively charged due to their phosphate backbone. This is a crucial point because it determines the direction of movement in an electric field.
3. In an electric field, negatively charged DNA will migrate towards the positive electrode (anode). This is because opposite charges attract.
4. Consider the structure of the gel, which acts as a sieve. Smaller DNA fragments move faster and further through the gel matrix than larger ones.
5. Eliminate incorrect options: DNA does not move towards the negative electrode, as it is negatively charged. It does not move randomly or remain stationary, as these do not align with the principles of electrophoresis.