Question

How to quantify the amount of dsDNA when i know the absorbances at 260 and 280 nm given i diluted 20 microlitres of DNA sample to 1000 microlitres???

Answer 1

@shrutipande9

Answer 2

Use the A260/A280 ratio to quantify the purity of the DNA sample (pure DNA has a A280/A260 of ~1.8).
For [dsDNA] in the diluted sample, use
A260 = (0.020)(C)(1) (where l = 1cm in most cases).
Then multiply C by 50 (you have diluted the sample by 50 times) to get the original [dsDNA] in the undiluted sample.

An important point - ensure that phenol is not used in the extraction procedure as this will greatly impact the accuracy of the results obtained.

Answer 3

So you are telling me to do this:
[dsDNA] = A260 X Dilution factor X 50
= A260 X 50 X 50

Answer 4

Yes, you're correct.