You isolate DNA from an organism using a standard protocol and have a final volu

Question

You isolate DNA from an organism using a standard protocol and have a final volume of 2.2 mL. You measure OD260 and OD280 for your sample on a UV spectrophotometer and get 0.477 and 0.261, respectively. (Remember an OD260 of 1.0 is equivalent to a concentration of 50 g/mL for pure dsDNA). Calculate both the concentration of DNA in your sample (g/mL), total yield of DNA (in g), as well as the 260/280 ratio for this sample

[DNA concentration] = __________
Total DNA = __________
260/280 ratio = _________

Explanation / Answer

Given that The concentration of double-stranded DNA with an A260 of 1.0 is 50 mg/ml. Thus, one can use the following formula to determine the DNA concentration of a solution.

Unknown (ug/ml) = 50 (ug/ml)/ 1.0 A260 x Absorbance measured at 260nm

=50 x 0.477

=23.85ug/ml

Total DNA = 23.85ug/ml x 2.2ml

= 52.47ug

260/280 ratio = 0.477/0.261

=1.828

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