Question

1. calculate the volume in ml of 50x protease required to make 2.0 l of 2x protease solution.
2. calculate the mass in grams of agarose to prepare a 2.5% agarose in 40 ml of 1x tae buffer. report your answer to two decimal places.
3. calculate the volume of 6x loading dye needed to run 15μl of dna sample by gel electrophoresis. note the loading dye is always at 1x concentration. report the answer to one decimal place with the correct units.

Explanation:

2.

Step1: Use dilution formula

$C_1V_1 = C_2V_2$. Here $C_1 = 50X$, $C_2=2X$, $V_2 = 2.0\ L=2000\ mL$.

Step2: Solve for $V_1$

$V_1=\frac{C_2V_2}{C_1}=\frac{2X\times2000\ mL}{50X}=80\ mL$.

3.

Step1: Use percentage - mass formula

Percent by mass $=\frac{\text{mass of solute}}{\text{volume of solution}}\times100\%$. Given percent by mass = 2.5%, volume of solution = 40 mL.

Step2: Solve for mass of agarose

Mass of agarose $=\frac{2.5\% \times40\ mL}{100\%}=1.00\ g$.

4.

Step1: Use dilution concept

For a 6X loading dye to achieve 1X, if the volume of DNA sample is $V_{DNA}=15\ \mu L$. Let the volume of 6X loading dye be $V$. Then $6V=(V + 15\ \mu L)\times1$.

Step2: Solve for $V$

$6V=V + 15\ \mu L$, $5V=15\ \mu L$, $V = 2.5\ \mu L$.

Answer:

2.

80 mL

3.

1.00 g

4.

2.5 μL