Multiple Choice
In gel electrophoresis, what is a DNA ladder used for?
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18. Molecular Genetic Tools
Methods for Analyzing DNA
Multiple Choice
In gel electrophoresis, what is the primary purpose of a DNA ladder (molecular weight marker)?
A
To stain DNA so bands become visible under UV light
B
To provide a set of DNA fragments of known sizes so the sizes of sample DNA bands can be estimated by comparison
C
To cut DNA at specific recognition sequences to generate restriction fragments
D
To amplify a specific DNA region through repeated cycles of denaturation, annealing, and extension
Verified step by step guidance1
Understand that gel electrophoresis is a technique used to separate DNA fragments based on their size by applying an electric field to a gel matrix.
Recognize that after running the gel, DNA fragments appear as bands, but their exact sizes are unknown without a reference.
Know that a DNA ladder (also called a molecular weight marker) contains DNA fragments of known lengths, which serve as a standard for comparison.
By running the DNA ladder alongside the sample DNA, you can compare the migration distances of sample bands to those of the ladder bands.
Use this comparison to estimate the sizes of the unknown DNA fragments in the sample by matching their positions to the corresponding bands in the ladder.
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