When DNA extraction and isolation is completed, it is typical to ascertain how m

Question

When DNA extraction and isolation is completed, it is typical to ascertain how much DNA was successfully extracted. To do this, a sample of the extract is diluted and Placed into a UV-Visible spectrometer. A spectrum is collected and the graph evaluated at a specific wavelength. ( You will only have one attempt at each of these questions) What is the wavelength? nm Why do we look at this specific wavelength? The absorption properties of DNA can be used for detection, quantification and assessment of purity. The wavelength of maximum absorption for both DNA and RNA is 280 nm (lambda_max = 280 nm) with a characteristic value for each base. The wavelength of maximum absorption for both DNA and RNA is 260 nm (lambda_max = 260 nm) with a characteristic value for each base. At a concentration of 1 mu g/mL and a 1 cm path length, ds DNA has A_260 = 50.

Explanation / Answer

answer is d

At a concentration of 1ug/ml and a 1 cm path length , dsDNA has A260=50

Usually absorbance is measured at 260 nm, at which wave length an absorbance of 1.0 corresponds to 50 µg of double-stranded DNA per ml. UV absorbance can also be used to check the purity of a DNA preparation. With a pure sample of DNA the ratio of the absorbancies at 260 nm and 280 nm (A260/A280) is 1.8. Ratios of less than 1.8 indicate that the preparation is contaminated, either with protein or with phenol.

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