Question

What is the dilution factor if 2 μl of DNA sample is added to 498 μl of water (Dilution factor = Final volume / Aliquot volume)? If the A260= 0.2 for the diluted sample, what is the concentration of DNA in the undiluted sample in μg/μl

Answer 1

Answer:

The correct answers are: Dilution factor = 250 and concentration of DNA in undiluted sample = 2.5 μg/μl.

Explanation:

• Volume of DNA taken = 2 μl.
• Volume of added water = 498 μl.
• Total volume of the sample = 2 μl + 498 μl = 500 μl.
• Dilution factor = $\frac{Final Volume}{Aliquot volume} = 500\div2 = 250.$
• A₂₆₀ of the given sample is = 0.2.
• We know that 50 μg/ml concentration of pure double stranded DNA gives an absorbance, A₂₆₀ = 1.
• Again, Concentration of DNA(µg/ml) = $A_{260}\times \texrm{dilution factor}\times 50$ µg/ml.
•                                                             = $0.2\times\ 250\times 50 = 2500$ μg/ml.
• In order to convert it into μg/μl, we have to divide the above value by 1000, hence we get, $2500\div1000 =2.5$ μg/μl.