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An agarose gel after electrophoresis shows three distinct DNA bands located at different distances from the wells. Band I is located closest to the wells, Band II is in the middle, and Band III is located farthest from the wells. Based on this observation, which of the following inferences is correct?

Options

  1. ABand III contains the largest DNA fragments among the three bands.
  2. BThe DNA fragments in Band I moved the fastest through the agarose gel.
  3. CBand III contains the smallest DNA fragments among the three bands.
  4. DThe fragments in Band I are positively charged, whereas those in Band III are negatively charged.

Correct answer

C. Band III contains the smallest DNA fragments among the three bands.

Step-by-step solution

During agarose gel electrophoresis, DNA fragments separate according to their size due to the sieving effect of the agarose gel. The smaller the fragment size, the farther it moves from the well. Since Band III is located farthest from the wells, it must contain the smallest DNA fragments. Band I, being closest to the wells, contains the largest DNA fragments and moved the slowest. All DNA fragments are negatively charged and move towards the anode; separation is based purely on size, not differences in charge. The

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