How does agarose concentration influence the separation of DNA fragments in gel electrophoresis?

How does agarose concentration influence the separation of DNA fragments in gel electrophoresis?

• A. Higher agarose concentration improves resolution of larger fragments; lower concentration resolves smaller fragments.
• B. Higher agarose concentration reduces overall separation.
• C. Higher agarose concentration improves resolution of smaller fragments; lower concentration resolves larger fragments.
• D. Agarose concentration does not affect fragment separation.

Answer: (C)

Agarose concentration sets the pore size of the gel, which determines how DNA fragments of different sizes experience resistance as they migrate. A denser gel (higher concentration) has smaller pores, increasing the sieving effect and making the movement of small DNA fragments more sensitive to their size, so differences between small fragments are sharpened. Large fragments are already hindered by the gel, and making the gel denser adds less useful separation for them. A looser gel (lower concentration) has bigger pores, which reduces the sieving effect on small fragments but lets large fragments separate more distinctly. So, higher concentration improves resolution of smaller fragments, while lower concentration helps resolve larger fragments.

Agarose concentration sets the pore size of the gel, which determines how DNA fragments of different sizes experience resistance as they migrate. A denser gel (higher concentration) has smaller pores, increasing the sieving effect and making the movement of small DNA fragments more sensitive to their size, so differences between small fragments are sharpened. Large fragments are already hindered by the gel, and making the gel denser adds less useful separation for them. A looser gel (lower concentration) has bigger pores, which reduces the sieving effect on small fragments but lets large fragments separate more distinctly. So, higher concentration improves resolution of smaller fragments, while lower concentration helps resolve larger fragments.