Question

Your new <$1 million grant has afforded you the ability to isolate DNA from bacterial cells. You want to estimate how much DNA is present in your sample. You use 30 µL of sample, add 270 µL of buffer, and receive an A260 of 0.40 and A280 of 0.25. (You can use whichever method you prefer on (a) and (b), but be consistent for both.

a. (2 pt) Assuming the sample was pure, about how much double-stranded DNA was present in the original 1.5 µL of the sample? Show your work.

b. (2 pt) Is this solution likely to contain pure nucleic acids or is there contamination by proteins? Show your work and defend your yes or no answer.

Answer 1

a) As it is assumed in question that sample is pure, so we will go directly with A260 absorbance results that is 0.40. For 1 A260 absorbance conecentartion is about 50microgram/ml. We can calculate it for our absorbance by multiplying it by value given above.

0.40 A260 = 0.40* 50, which give 20 microgram/ml.

b) For a DNA to be pure ratio of A260/A280 should be equal to 1.8.

Here it is. 0.40/0.25 = 1.6

which indicates that DNA is contaminated and it contains it shows sample is contaminated with peotein. When can say this becaus me protein absorbe at A 280 so if ratio is small it means A 280 is greater.

If it was helpful give a thumps up