You extracted a sample of DNA and analyzed it using a Nanodrop spectrophotometer. You recorded the following absorbances and then corrected them to produce the following values:

Question

A260 = 0.80

A280 = 0.75

Calculate the quality of DNA in the sample using these corrected absorbance(s). Report your answer to two decimal places (e.g., 1.00, 1.11, etc.) and DO NOT include units.

Be sure that your work:

provides the A260 value
provides the A280 value
identifies the equation that you used to solve the problem,
identifies which numbers you substituted for which variables in the equation,
exhibits all the necessary steps needed to show the math used to solve this problem and provide an answer
Hint: An equation "equates" two entities. If you do not include two things separated by an "=", then you have not written an equation -- you will have simply written a mathematical operation.

Using the example from the previous question, is your DNA solution of good quality? Why or why not?

Answer 1

To assess the quality of the DNA sample, we can use the A260/A280 ratio. This ratio helps determine the purity of nucleic acids in the sample, particularly detecting protein contamination. The ideal A260/A280 ratio for pure DNA is typically around 1.8.

Given Data

• A260 = 0.80
• A280 = 0.75

Equation used:

\[ \text{Quality Ratio} = \frac{A260}{A280} \]

Substituting Values:

\[ \text{Quality Ratio} = \frac{0.80}{0.75} \]

Calculation Steps:

1. Calculate the ratio: \[ 0.80 \div 0.75 = 1.0667 \]

2. Round to two decimal places: \[ 1.07 \]

Final Answer:

1.07

Conclusion about DNA quality:

The A260/A280 ratio of 1.07 indicates that the sample is not of good quality. A ratio below 1.8 suggests that the sample may be contaminated with proteins or other contaminants, which could interfere with downstream applications like PCR or sequencing. Thus, it is advisable to further purify the DNA before using it for experimental purposes.