Question

Materials
Salmon sperm DNA (200μL at 0.5mg/mL)
Salmon sperm DNA (200μL of unknown concentration)

1. How would you prepare 500μL in water of each of the following DNA standard solutions from the DNA sample of known concentration: 0.0, 0.05, 0.025, 0.01, 0.005 and 0.0025mg/mL.

2. How would you prepare 500μL samples in water representing 1/4 and 1/10 dilutions of the unknown DNA sample.

Answer 1

Solution :-

We know the initial concentration using that we find the volume of the known concentration solution needed to make the solutions with desired concentrations

1. is the blank solution so only use 500 ul water

making 0.05 mg/ml solution

0.05 mg /ml * 500 ul / 0.5 mg/ml = 50 ul

So we need to use 50 ul solution of 0.5 mg/ml concentration and dilute it to total volume of 500 ul

Making 0.025 mg/ ml solution

0.025 mg /ml * 500 ul / 0.5 mg/ml = 25 ul

So we need to use 25 ul solution of 0.5 mg/ml concentration and dilute it to total volume of 500 ul

Making 0.01 mg/ml solution

0.01 mg /ml * 500 ul / 0.5 mg/ml = 10 ul

So we need to use 10 ul solution of 0.5 mg/ml concentration and dilute it to total volume of 500 ul

Making of 0.005 mg/ml solution

0.005 mg /ml * 500 ul / 0.5 mg/ml = 5 ul

So we need to use 5 ul solution of 0.5 mg/ml concentration and dilute it to total volume of 500 ul

Making of 0.0025 mg/ml solution

0.0025 mg /ml * 500 ul / 0.5 mg/ml = 2.5 ul

So we need to use 2.5 ul solution of 0.5 mg/ml concentration and dilute it to total volume of 500 ul

2. How would you prepare 500μL samples in water representing 1/4 and 1/10 dilutions of the unknown DNA sample.

Solution :-

We know the initial volume of the unknown is 200 ul lets assume its concentration is 1

Then to make the ¼ solution lets calculate the amount of the unknown concentration solution needed

¼ * 500 ul / 1 = 125 ul

So we need to use 125 ul of the initial solution and dilute it to total volume of 500 ul

Now to make the 1/10 solution lets calculate the volume of the initial solution needed

1/10 * 500 ul / 1 = 50 ul

So we need to use 50 ml of original unknown solution and dilute it to total volume of 500 ul