Q.46 A forty-times diluted sample of ssRNA gave an 𝐴₂₆₀ of 0.01 . The concentration
of the ssRNA before the dilution in μ𝑔/𝑚𝐿 was _____ (correct to the nearest
integer).

The concentration of the ssRNA sample before 40-times dilution is 16 μg/mL. This value is calculated using the standard A260 conversion factor for ssRNA and rounded to the nearest integer as required.

Calculation Method

Nucleic acid concentration from A260 absorbance uses the Beer-Lambert law, where an A260 of 1.0 corresponds to 40 μg/mL for ssRNA in a 1 cm pathlength cuvette. For a diluted sample, multiply the measured A260 by the ssRNA factor (40) and the dilution factor (40).

The formula is:
Concentration (μg/mL) = A260 × 40 × dilution factor

Here:
Concentration = 0.01 × 40 × 40 = 16 μg/mL

Step-by-Step Solution

1. Measured A260 of diluted sample: 0.01 (forty-times diluted).

2. ssRNA conversion: A260 = 1.0 equals 40 μg/mL undiluted.

3. Account for dilution: Original concentration = diluted A260 × 40 × 40 = 16 μg/mL.

4. Round to nearest integer: 16 (no change needed).

This matches CSIR NET/GATE Life Sciences standards for spectrophotometric quantification.

Single-stranded RNA (ssRNA) concentration calculation from A260 absorbance is a core skill for CSIR NET Life Sciences aspirants tackling spectrophotometry questions. This guide breaks down the exact method for a forty-times diluted ssRNA sample with A260 of 0.01, yielding 16 μg/mL before dilution—perfect for exam prep in molecular biology and biochemistry.

Key Formula for ssRNA A260

Use Concentration (μg/mL) = A260 × 40 × dilution factor for ssRNA, as 1 A260 unit equals 40 μg/mL undiluted. This differs from dsDNA (50 μg/mL) or ssDNA (33-37 μg/mL), emphasizing nucleic acid type in calculations.

Detailed Worked Example

• Diluted A260 reading: 0.01

• Dilution factor: 40

• ssRNA factor: 40 μg/mL per A260 unit

• Result: 0.01 × 40 × 40 = 16 μg/mL (nearest integer).

Common Pitfalls to Avoid:

• Wrong factor: Using dsDNA’s 50 yields 20 μg/mL (incorrect for ssRNA).

• Ignoring dilution: 0.01 × 40 = 0.4 μg/mL mistakes diluted for original.

• Units: A260 assumes 1 cm pathlength; adjust if microvolume (e.g., NanoDrop).

• Purity check: Ideal A260/A280 is 2.0 for RNA; low values indicate contamination.

CSIR NET Relevance

This mirrors PYQ styles testing UV spectroscopy in biotechnology. Practice with tools like Python for precision: 0.01 * 40 * 40 confirms 16.

Master ssRNA A260 to μg/mL conversions for competitive edges in genetics and biochemistry sections.