Question

Question 5 Using stock solutions in a protocol: from volume to final concentration
A reverse transcription reaction is carried out in a 30 μL reaction mix. This type of reaction is carried out to convert RNA to complementary DNA. You are going to set up a number of these reactions so you decide to make up a larger volume of the reaction mixture, called a master mix. This saves on multiple repetitive pipetting and reduces errors. You have been given a protocol to make up 1 mL of this reverse transcription master mix and it states that you must add 3 μL of a 50 mM nucleotide mix (dNTPs).
 What is the final concentration of dNTPs in the reaction mixture?
 You need to do 30 reverse transcription reactions. Do you have enough reaction mixture?

Answer 1

3 μL of a 50 mM nucleotide mix is needed for 1 ml of master mix.

We have to prepare 30μL of master mix. Therefore, the final conc of dNTPs added can be found out by V1S1=V2S2,

or, 3 μL*50 mM = 1000μL * S2

S2= o.15 mM of dNTPs.

Again for 1 reaction cycle, 30 μL reaction mix is needed. To carry out 30 reaction cycles, the total reaction mix would be 30* 30 μL= 900 μL. So 1 ml of master mix is sufficient.