To extract DNA from a tissue sample, you need to prepare 500 ml extraction buffe
ID: 571211 • Letter: T
Question
To extract DNA from a tissue sample, you need to prepare 500 ml extraction buffer. You have thefollowing components, along with water:
Stocks
3 M NaCl
10% (w/v) sodium dodecyl sulfate
20 mg/ml Proteinase K
You need your extraction buffer to contain:
Final
30 mM NaCl
0.2% (w/v) sodium dodecyl sulfate
1.5 mg/ml Proteinase K
How much of each is needed to make your extraction buffer? How much water is needed?
Amount needed: Component:
____________ 3 M NaCl
____________ 10% (w/v) sodium dodecyl sulfate
____________ 20 mg/ml Proteinase K
____________ water
Explanation / Answer
We shall use the dilution equation
C1*V1 = C2*V2 where C1 = concentration of stock solution, V1 = volume of stock solution, C2 = concentration of the final solution and V2 = volume of the final solution.
NaCl
(3 M)*V1 = (30 mM)*(500 mL)
====> V1 = (30 mM)*(500 mL)/(3 M) = (30 mM)*(1 M/1000 mM)*(500 mL)/(3 M) = 5 mL.
Sodium Dodecyl sulfate
(10% w/v)*V1 = (0.2% w/v)*(500 mL)
====> V1 = (0.2% w/v)*(500 mL)/(10% w/v) = 10 mL.
Proteinase K
(20 mg/mL)*V1 = (1.5 mg/mL)*(500 mL)
====> V1 = (1.5 mg/mL)*(500 mL)/(20 mg/mL) = 37.5 mL.
The volume of water required = [500 – (5 + 10 + 37.5)] mL = 447.5 mL.
The solution is prepared by adding 5 mL of 3M NaCl, 10 mL of 10% (w/v) sodium dodecyl sulfate and 37.5 mL of 20 mg/mL Proteinase K to a 500 mL volumetric flask and making up the volume to the mark with water.