Question

You extracted DNA and recorded the absorbance at two wavelengths. A260= .7 and A280= .39.

A) is your DNA pure?

B) Determine the concentration of your DNA, knowing that 50 ug/ml DNA has an absorbance of 1 at 260nm.

Answer 1

Absorbance of extracted DNA at A260 = 0.7 and A 280 = 0.39

A. To estimate purity of extracted DNA we can use ratio A260/A280.

Ratio value of ~1.8 indicate good quality DNA, if value is around 2, it indicates RNA contamination. If value is lower than 1.7 indicates presence of contaminants (proteins)

Absorbance at A260 / Absorbance at A280 = 0.7 / 0.39 = 1.795. Thus we have DNA with good purity.

B. 50 microgram/ mL DNA has absorbance of 1 at 260 nm. We have 0.7 absorbance for DNA at 260 nm.

Concentration DNA =(50g/mL) * (Absrbance at 260 nm) * (Dilution factor)

Concentration DNA =(50g/mL) * (0.7) * (1) = 35g/mL

(Note: dilution factor is not provided, so consider it as 1, indicating no dilution)

Thus, concentration DNA is  35g/mL

Did this help? If yes, do give positive rating for this answer. Thank you!