PCR Primer Dilution from F+R - (Dec/02/2010 )

Ok, I have a question involving making a primer working stock by combining the F+R primer

So, I have my F and R primers seperately at 100micromolar. I want to make 200microliters of a 7.5micromolar working stock. When I set up C1V1=C2V2, I get: V1= <(7.5uM)(200ul)>/(100uM)= 15ul. However, does this 15ul actually mean 30ul since the F and R are seperately at 100uM? To perhaps clarify better, am I adding 7.5ul of the F and 7.5 of the R to 185ul of H20? Or, am I adding 15ul of Forward + 15 ul of Reverse to 170ul H20?

I would greatly appreciate any help.

Your second option is correct. If you want to have both primers together in one solution at 7.5 uM, you need to add 15 ul of each and then make up the difference with 170 ul of water.