Question

A sample you have analyzed with an agarose gel has the same apparent brightness as the nearby 42 ng/μL band of the standard ladder. If you loaded your entire sample that was prepared with 5 μL of plasmid DNA mixed 1:1 with loading dye, and you made the comparison to a ladder that used 2 μL of the standard solution, what is the concentration of your plasmid stock?

Answer 1

To determine the concentration of the plasmid stock, set up a proportion and solve for the concentration of your sample. The concentration of your plasmid stock is approximately 105 ng/μL.

Step-by-step explanation:

To determine the concentration of the plasmid stock, we need to compare the brightness of the sample band to the brightness of the 42 ng/μL band of the standard ladder. We know that you loaded 5 μL of your sample and 2 μL of the standard solution. Since the brightness is the same, we can assume that the concentrations are proportional.

Let's set up a proportion: (concentration of your sample) / (concentration of standard ladder) = (volume of your sample) / (volume of standard solution) Plugging in the values, we have: (concentration of your sample) / 42 ng/μL = 5 μL / 2 μL Simplifying, we can solve for the concentration of your sample: (concentration of your sample) = (42 ng/μL) * (5 μL / 2 μL) Calculating, the concentration of your plasmid stock is approximately 105 ng/μL.