Separating restriction fragments: Which electrophoretic media are commonly used to separate DNA fragments from a restriction digest?

Introduction / Context:After restriction digestion, DNA fragments are separated by size using electrophoresis. The choice of matrix depends on the fragment length range and resolution required.

Given Data / Assumptions:

• Agarose gels are suited for hundreds to many thousands of base pairs.
• Polyacrylamide gels offer higher resolution for small DNA fragments (tens to a few hundred base pairs).
• We are considering standard laboratory practice.

Concept / Approach:Agarose concentrates (e.g., 0.8–2%) are tuned to resolve larger fragments; polyacrylamide (PAGE) provides a tighter matrix for fine resolution of small fragments or single base differences (e.g., sequencing gels). Both are valid and widely used for restriction fragment analysis.

Step-by-Step Solution:Match fragment size range to gel type: large → agarose, small/high-resolution → PAGE.Recognize that both media are standard for separating DNA.Select “both (a) and (b).”

Verification / Alternative check:Protocols for plasmid mapping frequently use agarose; mutation detection or small fragment resolution often uses PAGE, confirming both are appropriate.

Why Other Options Are Wrong:

• A or B alone is incomplete because both are used depending on the application.
• None (D) contradicts routine practice.

Common Pitfalls:Using agarose to resolve very small fragments can blur bands; choosing incorrect acrylamide percentage can impair resolution for the target size range.

Final Answer:both (a) and (b)