During gel electrophoresis of DNA fragments, which statement is correct?
Answer and explanation
Correct answer: D. Fragments move towards the positive electrode, and shorter fragments move further
- Step 1: DNA has a negatively charged phosphate backbone, so it is attracted towards the positive electrode.
- Step 2: The gel acts as a mesh; short fragments pass through more easily and travel further.
Answer
Fragments move towards the positive electrode, and shorter fragments move further.
Why not the others: Fragments move towards the negative electrode, and longer fragments move further: DNA is negatively charged, so it moves towards the positive electrode. Fragments move towards the positive electrode, and longer fragments move further: larger fragments are slowed more by the gel. Fragments stay in place because DNA is neutral: DNA carries a negative charge from its phosphate groups.
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