Multiple Choice
In a standard DNA extraction protocol, why is detergent (e.g., SDS) added to the sample?
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18. Molecular Genetic Tools
Methods for Analyzing DNA
Multiple Choice
In agarose gel electrophoresis, why is bromophenol blue added to individual DNA samples before loading them into the gel?
A
It intercalates into DNA to increase fluorescence under UV light so bands can be seen without staining.
B
It digests contaminating proteins in the sample to prevent smearing in the gel.
C
It chemically denatures double-stranded DNA into single strands to improve separation by size.
D
It serves as a tracking dye to monitor sample migration during electrophoresis and helps visualize loading progress.
Verified step by step guidance1
Understand the purpose of loading dyes in agarose gel electrophoresis, which is to help track the progress of DNA migration through the gel during the run.
Recognize that bromophenol blue is a common tracking dye added to DNA samples before loading them into the gel.
Know that bromophenol blue does not interact chemically with DNA to alter its structure or fluorescence; instead, it migrates through the gel at a predictable rate.
Realize that the dye's migration allows researchers to estimate how far the DNA fragments have traveled without waiting for staining or UV visualization.
Conclude that bromophenol blue helps visualize the loading process and monitor electrophoresis progress, ensuring samples are properly loaded and run for an appropriate time.
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