What is the purpose of a DNA ladder or molecular weight marker in gel electrophoresis?

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BlackTom AI · Accepted Answer

When considering the purpose of a DNA ladder or molecular weight marker in gel electrophoresis, we first look at how size estimation is performed in this technique.
Option 1: 'To amplify DNA samples' This is incorrect because ladders are not involved in amplification; PCR uses primers and polymerases, not a DNA ladder as a reference. The ladder itself does not boost or replicate DNA.
Option 2: 'To provide a reference for estimating the sizes of DNA fragments' This is the core role of a ladder. It contains fragments of known lengths, which run alongside samples so you can compare bands and deduce approximate sizes.
Option 3: 'To color the gel' While some gels use dyes for visualization, the ladder's primary function is not coloring; dyes used for loading or visualization do not define fragment sizes.
Option 4: 'To improve gel resolution' The ladder does not inherently improve resolution; resolution depends on gel composition, electrophoresis conditions, and sample quality. The ladder’s job is reference sizing, not sharpening separation.

In summary, the ladder serves as a calibration tool that allows researchers to translate the distance migrated in the gel into an estimated fragment size by comparing to the known standards, making option 2 the correct description of its purpose.

BIOL2309.13196.202610 Exam - Multiple Choice Part- Requires Respondus LockDown Browser

What is the purpose of a DNA ladder or molecular weight marker in gel electrophoresis?

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