Question

To detect the DNA band in your gel, you need to add ethidium bromide (EtBr) from a concentrated stock solution (40 ug/ml) to get a final concentration of 5 ug/ml in your agarose solution. Unfortunately, you made your agarose solution (0.8% agarose and 50 ml volume) before adding the EtBr. Thus, when you add he appropriate volume of concentrated EtBr, you will increase the fila volume of agarose solution.

a. What volume of the concentrated EtBr must you add to the 50 ml solution of agarose to end up with your desired final concentration of 5 ug/ml EtBr?

its not 6.25 ml

b. What is the new volume of the agarose solution?

c. What is the resulting concentration of agarose after you’ve added the EtBr?

Answer 1

Concentration of EtBr Stock solution : 40ug/ml

Required Final concentration of EtBr in Agrose solution : 5ug/ml

a. The Answer Is calculated from following Equation:

C₁V₁ = C2V₂

C₁ is Concentration of Stock Solution = 40 ug/ml

V₁ is volume of Stock Solution to make final concentration.

C₂ is required final concentration = 5ug/ml

V₂ is required final volume = 50 ml

Final Answer is 6.25ml of stock solution is required to make final concentration 5 ug/ml

b.

The new volume of Agarose solution is 56.25ml because 6.25 ml EtBr is added in 50 ml of agarose solution.

c.

The resulting Concentration of Agarose in new final solution is 0.9%.