Resolving power: About how large a DNA fragment can be resolved by standard agarose gel electrophoresis versus pulsed-field gel electrophoresis (PFGE), respectively?

Introduction / Context:Agarose gels and PFGE are complementary techniques for sizing DNA. Choosing the right platform prevents smearing and allows accurate comparison to size markers, especially for large chromosomal fragments.

Given Data / Assumptions:

• Standard horizontal agarose electrophoresis under typical field strengths.
• PFGE alternates field orientation to reorient large DNA molecules.
• We compare practical, order-of-magnitude limits.

Concept / Approach:Conventional agarose effectively resolves fragments up to roughly 15–25 kb (gel conditions dependent). PFGE extends resolution into the megabase range by periodically switching the electric field to allow reptation of very large DNA.

Step-by-Step Solution:Set a representative upper bound for standard agarose → about 20 kb.Set a representative upper bound for PFGE → about 2000 kb (2 Mb).Match to the option that states 20 kb and 2000 kb.

Verification / Alternative check:PFGE is routinely used to separate large restriction fragments of bacterial chromosomes and yeasts in the 100 kb–2 Mb range.

Why Other Options Are Wrong:

• Orders swapped or unrealistic for either technique.
• Values like 10 kb for agarose are too restrictive; 2000 kb for standard agarose is not attainable.

Common Pitfalls:Assuming higher agarose concentration increases upper size limit; it actually favors smaller fragments, not megabase DNAs.

Final Answer:20 kb and 2000 kb DNA