Exercise 14.3 - Characterization of dna
- DNA sample
- SSC buffer
- UV spectrophotometer 3
and quartz cuvettes
- Dissolve a small quantity of your extracted DNA in 3.0 ml of
- Turn on and blank a UV spectrophotometer at 220 nm (use 0.1X
SSC as the blank). Determine the absorbance of your sample DNA
at 230 nm.
- Change the wavelength to 230 nm, reblank the spectrophotometer
and measure the absorbance of the sample at 230 nm.
- Increment the wavelength by 10 nm and repeat blanking and
measuring the absorbance until readings are taken through 300 nm.
- Compute the absorbance ratio 260 nm to 280 nm. Pure DNA
(without protein or RNA) will have a 260:280 absorbance ratio of
1.85. RNA will have a 260:280 ratio of 2.0.
- Plot the absorbance spectrum of your sample and indicate the
260:280 ratio, as well as the amount of protein contamination on
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Cell Biology Laboratory Manual
Dr. William H. Heidcamp, Biology Department, Gustavus Adolphus College,
St. Peter, MN 56082 -- firstname.lastname@example.org