Laboratory methods: DNA agarose gel electrophoresis and protein SDS–PAGE are similar in which fundamental ways during biomolecule separation by gels?

Introduction:
Agarose gel electrophoresis for DNA and SDS–PAGE for proteins are cornerstone techniques for separating biomolecules by size. Despite analyzing different macromolecules with different gel matrices, they share several core physical principles. This question asks you to identify the commonalities that make these methods conceptually similar in the lab.

Given Data / Assumptions:

• An applied electric field drives migration of charged macromolecules through a hydrated gel matrix.
• DNA carries a nearly uniform negative charge per unit mass due to the phosphate backbone.
• In SDS–PAGE, sodium dodecyl sulfate coats proteins, conferring a near-constant negative charge-to-mass ratio.
• Gels (agarose or polyacrylamide) act as molecular sieves that hinder larger molecules more than smaller ones.

Concept / Approach:
Both assays separate primarily by size because the charge-to-mass ratio is roughly constant across species being compared. DNA is inherently uniformly charged; proteins become uniformly charged after SDS binding and denaturation. Under standard electrophoresis setups, negatively charged samples migrate toward the positively charged electrode (the anode). The hydrated gel network provides steric hindrance, so smaller molecules negotiate the pores more readily and run farther for a given time and voltage.

Step-by-Step Solution:

Verification / Alternative check:
Marker ladders (DNA size standards or protein prestained ladders) resolve into predictable bands whose migration is logarithmically related to size under constant buffer, gel concentration, and voltage—consistent with sieving plus constant charge-to-mass assumptions.

Why Other Options Are Wrong:

• Claiming no electric field is used is incorrect; electrophoresis literally requires an electric field.
• Suggesting only one of the features is shared ignores that all listed similarities apply under standard conditions.

Common Pitfalls:
Confusing native PAGE (variable charge) with SDS–PAGE (normalized charge), or assuming DNA might migrate to the cathode; in typical TAE/TBE systems, DNA runs to the anode because it is negatively charged.

Final Answer:
All of the above