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Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Pure DNA fragments separated on an agarose gel cannot be seen under visible light. Reason (R): Staining the DNA fragments with ethidium bromide allows them to be visualised as bright orange bands when exposed to visible light. In the light of the above statements, choose the most appropriate answer

Options

  1. ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
  2. BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
  3. C(A) is correct but (R) is not correct
  4. D(A) is not correct but (R) is correct

Correct answer

C. (A) is correct but (R) is not correct

Step-by-step solution

According to NCERT, pure DNA fragments cannot be seen under visible light and without staining. Hence, Assertion (A) is correct. To visualise the separated DNA fragments, they must be stained with a compound known as ethidium bromide followed by exposure to ultraviolet (UV) radiation. They cannot be seen under visible light even after staining. Exposure to UV radiation reveals bright orange coloured bands of DNA. Hence, Reason (R) is incorrect. Answer: (A) is correct but (R) is not correct

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