Virtual Labs

Analyse quality and quantity of DNA, RNA

What is the principle behind UV spectrophotometry for DNA quantification?

a: Measurement of light scattering by DNA molecules Explanation

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b: Measurement of absorbance of UV light by nucleic acids at 260 nm Explanation

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c: Measurement of fluorescence of ethidium bromide-bound DNA Explanation

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d: Measurement of color change due to DNA–protein interaction Explanation

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Which wavelength is used to measure DNA concentration?

a: 230 nm Explanation

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b: 260 nm Explanation

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c: 280 nm Explanation

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d: 325 nm Explanation

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An A₂₆₀ of 1.0 corresponds to how much double-stranded DNA in 1 mL of solution?

a: 10 µg/mL Explanation

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b: 25 µg/mL Explanation

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c: 50 µg/mL Explanation

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d: 100 µg/mL Explanation

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Which ratio indicates high-purity DNA with minimal protein contamination?

a: A₂₆₀/A₂₈₀ = 1.0 Explanation

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b: A₂₆₀/A₂₈₀ = 1.5 Explanation

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c: A₂₆₀/A₂₈₀ = 1.8-1.9 Explanation

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d: A₂₆₀/A₂₈₀ = 2.5 Explanation

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What does a low A₂₆₀/A₂₃₀ ratio (<1.5) indicate?

a: Presence of RNA Explanation

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b: Presence of chaotropic salts or organic contaminants Explanation

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c: Presence of degraded DNA Explanation

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d: Pure DNA sample Explanation

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Why should TNE buffer be used instead of water for DNA dilution?

a: It increases DNA absorbance artificially Explanation

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b: It maintains the pH precisely at 7.4 Explanation

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c: It reacts with proteins to improve purity Explanation

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d: It removes RNA contamination Explanation

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What type of cuvette must be used for UV spectrophotometry?

a: Glass cuvette Explanation

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b: Plastic cuvette Explanation

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c: Quartz cuvette Explanation

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d: Polystyrene cuvette Explanation

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Which factor can cause false high absorbance readings in UV spectrophotometry?

a: Cold samples Explanation

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b: Dirty cuvettes or particulate matter Explanation

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c: Overdilution of DNA Explanation

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d: Use of glass cuvettes Explanation

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What is the main function of ethidium bromide in gel electrophoresis?

a: xxx Explanation

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b: xxx Explanation

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c: xxx Explanation

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d: xxx Explanation

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xxx

a: To denature DNA Explanation

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b: To intercalate between DNA bases and fluoresce under UV light Explanation

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c: To act as a reducing agent Explanation

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d: To act as a DNA stabilizer Explanation

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DNA migrates toward which electrode during gel electrophoresis?

a: Negative Explanation

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b: Positive Explanation

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c: Both equally Explanation

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d: None of the above Explanation

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