Question

The 1% agarose gels you have used in lab are optimal for separating 0.5~10 kb DNAs by size. How would you modify your gel if you wanted to separate a 30 kb plasmid?

A. Lower the voltage
B. Run the gel for a longer time
C. Increase the voltage
D. Lower the agarose gel density
E. No need to modify

Answer 1

To separate a 30 kb plasmid using agarose gel electrophoresis, the agarose gel density should be lowered to increase the pore size, allowing the larger DNA fragments to migrate through the gel. This means option D is the correct modification needed.

Step-by-step explanation:

If we wanted to separate a 30 kb plasmid using agarose gel electrophoresis, we need to modify the pore size of the gel to accommodate the larger size of the DNA fragments. The pore size is directly related to the percentage of agarose in the gel: a higher percentage creates a gel with smaller pores appropriate for separating smaller DNA fragments, while a lower percentage results in larger pores for larger DNA fragments.

Therefore, the best approach would be to lower the agarose gel density for separating a 30 kb plasmid, meaning option D is correct. Lowering the agarose concentration will increase pore size, allowing the larger plasmid to move more easily through the gel matrix.