Multiple Choice
Which two components make up the backbone of the DNA double helix?
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7. DNA and Chromosome Structure
DNA Structure
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Why does DNA migrate toward the positive electrode during gel electrophoresis?
A
Because the gel matrix repels DNA toward the positive side
B
Because DNA molecules have a negatively charged phosphate backbone
C
Because DNA is neutral and moves randomly in the electric field
D
Because DNA is attracted to the negative electrode due to its positive charge
Verified step by step guidance1
Understand the basic principle of gel electrophoresis: molecules are separated based on their size and charge by applying an electric field across a gel matrix.
Recall the chemical structure of DNA, focusing on the phosphate groups in its backbone, which carry a negative charge due to their ionized phosphate groups.
Recognize that because DNA has a net negative charge, it will be attracted to the positive electrode (anode) when an electric field is applied.
Note that the gel matrix acts as a sieve, allowing smaller DNA fragments to move faster, but it does not repel DNA; the direction of movement is determined by charge.
Conclude that DNA migrates toward the positive electrode during gel electrophoresis because its negatively charged phosphate backbone is attracted to the positive charge.
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