A classmate has asked you to help them determine the concentration of DNA in their solution. Their A260 reading was 1.69. What was the concentration of their DNA

Acid , phenol or protein

Explanation:

The ratio of absorbance at 260 and 280nm is what is usually used to assess the purity which a DNA or RNA posses. A ratio of 1.8 is generally accepted as being pure for a DNA sample and a ratio of 2.0 is generally accepted also as being pure for RNA. when the ratio is significantly lower in each case, it indicates that there is presence of protein, phenol or other contaminants.