Virtual Labs

Analyse quality and quantity of DNA, RNA

During the UV spectrophotometric analysis, a DNA sample showed an A₂₆₀/A₂₈₀ ratio of 1.45. What does this indicate?

a: The DNA is pure and intact Explanation

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b: The DNA is contaminated with RNA Explanation

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c: The DNA sample has protein contamination Explanation

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d: The DNA concentration is too low Explanation

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Which of the following statements is true regarding the purity of nucleic acids?

a: RNA and DNA both absorb maximally at 280 nm Explanation

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b: The A₂₆₀/A₂₃₀ ratio indicates protein contamination Explanation

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c: A₂₆₀/A₂₈₀ ratio of ~2.0 suggests pure RNA Explanation

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d: A₂₆₀/A₂₈₀ ratio below 1.0 indicates very pure DNA Explanation

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The absorbance at 230 nm primarily reflects contamination from:

a: Proteins Explanation

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b: Salts, organic solvents, and chaotropic agents Explanation

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c: RNA Explanation

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d: Agarose Explanation

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In agarose gel electrophoresis, intact chromosomal DNA appears as:

a: A sharp, single band near the top of the gel Explanation

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b: A diffuse smear Explanation

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c: Multiple sharp bands of different sizes Explanation

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d: A faint streak near the bottom Explanation

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If DNA bands appear as a smear rather than discrete bands, what is the most likely reason?

a: Overloading of the sample Explanation

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b: Degradation of DNA Explanation

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c: Incorrect buffer concentration Explanation

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d: High-purity DNA Explanation

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The direction of DNA movement in agarose gel electrophoresis is due to:

a: Positive charge on the phosphate backbone Explanation

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b: Negative charge on the phosphate backbone Explanation

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c: Neutral charge on the sugar-phosphate backbone Explanation

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d: Charge from ethidium bromide binding Explanation

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During electrophoresis, why are samples mixed with loading dye before being loaded into wells?

a: To stain the DNA Explanation

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b: To increase DNA concentration Explanation

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c: To make the sample denser and visible during loading Explanation

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d: To digest RNA contamination Explanation

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A student obtained fluctuating readings on the spectrophotometer. The most probable cause is:

a: Low DNA concentration Explanation

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b: Excessive light scattering Explanation

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c: RNA contamination Explanation

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d: Ethidium bromide presence Explanation

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Which of the following statements best explains the principle of agarose gel electrophoresis?

a: DNA fragments are separated according to their charge density Explanation

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b: DNA fragments are separated based on molecular weight and size Explanation

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c: DNA fragments are separated by sequence composition Explanation

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d: DNA fragments move randomly through the gel Explanation

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What safety precaution must be observed when using ethidium bromide?

a: Avoid exposure to UV light Explanation

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b: Use nitrile gloves and dispose of gels properly as hazardous waste Explanation

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c: Mix it with buffers before heating Explanation

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d: It is safe to use without PPE Explanation

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