8. The purity of DNA extractions is measured by calculating the ratio between th

Question

8. The purity of DNA extractions is measured by calculating the ratio between the absorbance peak of DNA (A260) and the absorbance peaks of com like proteins which have a peak absorbance at 280 nm (Aza0), or chaotropic salts which absorb strongly at 230 nm (A230). For DNA, an Azo/A2so ratio of-18 and/or an Az6o/Az30 ratio of 1.8-2.2 is generally accepted as "pure". What are the Azso and A230 OD values for your DNA extraction? Based on these values, how pure is your DNA extraction (show your work)? If it isn't pure, what do the ratios indicate are contaminating your extraction? (4 points) mon contaminants

Explanation / Answer

A230 = 0.641, A260 = 0.893, A280 = 0.444

A260/A280 = 0.893/0.444 = 2.0112612613

The obtained value is higher than 1.8, it indicates DNA is free from protein contamination (values lower than 1.8 indicates protein contamination).

A260/A230 = 0.893/0.641 = 1.3931357254

The obtained value is lower than 1.8, it indicates that DNA is contaminated with salts or some solvents such as phenol.

The DNA should be re-purified by ethanol precipitation followed by re-suspension into TE buffer.

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