Multiple Choice
In which direction does DNA move during agarose gel electrophoresis, and why?
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18. Molecular Genetic Tools
Methods for Analyzing DNA
Multiple Choice
In agarose gel electrophoresis, in which direction does DNA migrate and why?
A
Toward the negative electrode (cathode) because DNA is positively charged at neutral pH.
B
Toward whichever electrode is closest because migration is driven primarily by diffusion, not charge.
C
DNA does not migrate in an electric field; it remains in the wells unless heated.
D
Toward the positive electrode (anode) because the phosphate backbone gives DNA a net negative charge.
Verified step by step guidance1
Understand the basic principle of agarose gel electrophoresis: DNA molecules are placed in a gel matrix and subjected to an electric field, which causes them to migrate based on their charge.
Recall that DNA has a phosphate backbone, which carries a negative charge at neutral pH. This means DNA molecules are negatively charged overall.
Since opposite charges attract, DNA will migrate toward the positive electrode, also called the anode, during electrophoresis.
Recognize that the migration direction is not random or due to diffusion but is driven by the electric field acting on the charged DNA molecules.
Summarize that DNA moves from the wells toward the positive electrode because the negative charge on DNA is attracted to the positive charge of the anode.
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