Multiple Choice
Ethanol is used in the DNA isolation process because it primarily:
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18. Molecular Genetic Tools
Methods for Analyzing DNA
Multiple Choice
In agarose gel electrophoresis, what can a DNA ladder (molecular weight marker) help determine about the DNA fragments in a sample?
A
The exact nucleotide sequence of each DNA fragment
B
The precise concentration (ng/µL) of DNA in the sample without any additional standards
C
Whether the DNA is single-stranded or double-stranded based on base pairing
D
The approximate size (length in base pairs) of the DNA fragments by comparison to bands of known size
Verified step by step guidance1
Understand that a DNA ladder, also called a molecular weight marker, consists of DNA fragments of known sizes (measured in base pairs).
During agarose gel electrophoresis, DNA fragments in the sample and the DNA ladder are loaded into separate wells and subjected to an electric field, causing them to migrate through the gel.
Smaller DNA fragments move faster and travel farther through the gel, while larger fragments move slower and remain closer to the wells.
By comparing the distance traveled by the sample DNA fragments to the distances traveled by the bands in the DNA ladder, you can estimate the size (length in base pairs) of the sample fragments.
Note that the DNA ladder does not provide information about the exact nucleotide sequence, concentration without standards, or strand status (single vs. double-stranded); its primary use is size estimation.
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