Question

When adding your DNA samples to the agarose gel, you will need to add loading dye to the samples. Loading dye contains: ¥ glycerol, which helps the samples sink into the sample wells of the gel; and ¥ tracking dyes so that you have a way of estimating how far the samples have travelled through the gel during electrophoresis. The recipe for 6X loading dye is as follows: ¥ 0.25% bromophenol blue (w/v) ¥ 0.25% xylene cyanol (w/v) ¥ 30% glycerol in water (v/v) 11. Provide a recipe for 10 ml of 10X loading dye, using the information above. (Important tip: Remember that you have already made 30ml of a 50% stock solution of glycerol. I recommend determining the concentration of glycerol required for 10X loading dye, then figuring out how much of your 50% glycerol stock will be needed to make 10ml of 10X loading dye.)

Answer 1

6X loading dye composition:

0.25% bromophenol blue (w/v)

0.25% xylene cyanol (w/v)

30% glycerol in water (v/v)

Required volume = 10 mL

Required concentration = 10X

i. 0.25% bromophenol blue (w/v)

1 g in 10 mL = 10%

0.1 g in 10 mL = 1%

0.025 g in 10 mL = 0.25%

ii. 0.25% xylene cyanol (w/v)

1 g in 10 mL = 10%

0.1 g in 10 mL = 1%

0.025 g in 10 mL = 0.25%

iii. 30% glycerol in water (v/v)

Stock = 50%

1 mL in 10 mL = 5%

6 mL in 10 mL = 30%

Take 3 mL of distilled water. Add required amounts of Bromophenol blue and xylene cyanol. Mix them completely. Then add 6 mL of 50% glycerol. Mix well. Make up the volume to 10 mL with water.