Multiple Choice
In agarose gel electrophoresis, how are DNA fragments primarily separated?
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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 DNA fragments in a sample?
A
The approximate size (length in base pairs) of the DNA fragments by comparison to known standards
B
Whether the DNA fragments are single-stranded or double-stranded based solely on ladder position
C
The number of restriction enzyme recognition sites present in each fragment without additional analysis
D
The exact nucleotide sequence of each DNA fragment
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 migrate through the gel matrix at rates inversely proportional to their size; smaller fragments move faster and farther than larger ones.
By running the DNA ladder alongside the sample, you create a reference scale that allows you to compare the migration distances of unknown DNA fragments to those of the ladder fragments.
Measure the distance each DNA fragment in the sample has traveled and compare it to the distances traveled by the ladder fragments to estimate the size of the sample fragments.
Note that the ladder does not provide information about strand type (single or double), number of restriction sites, or exact nucleotide sequence; it only helps approximate fragment size based on migration.
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