Question:
The purity of a plasmid DNA preparation is determined by analyzing the ratio \(A_{260}/A_{280}\). In a pure DNA preparation, the ratio will be
The purity of a plasmid DNA preparation is determined by analyzing the ratio \(A_{260}/A_{280}\). In a pure DNA preparation, the ratio will be
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• DNA purity → \(A_{260}/A_{280} \approx 1.8\)
• Lower value → Protein contamination
Updated On: May 13, 2026
- close to 2
- close to 1
- less than 1
- equal to 1
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The Correct Option is A
Solution and Explanation
Concept:
The ratio \(A_{260}/A_{280}\) is used to assess nucleic acid purity.
• \(A_{260}\): Absorbance of nucleic acids
• \(A_{280}\): Absorbance of proteins
Step 1: Understanding standard values.
• Pure DNA → Ratio $\approx$ 1.8 (close to 2)
• Pure RNA → Ratio $\approx$ 2.0
• Lower ratio → Protein contamination
Step 2: Selecting the correct answer.
Since pure DNA has a ratio around 1.8, it is close to 2.
• \(A_{260}\): Absorbance of nucleic acids
• \(A_{280}\): Absorbance of proteins
Step 1: Understanding standard values.
• Pure DNA → Ratio $\approx$ 1.8 (close to 2)
• Pure RNA → Ratio $\approx$ 2.0
• Lower ratio → Protein contamination
Step 2: Selecting the correct answer.
Since pure DNA has a ratio around 1.8, it is close to 2.
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