First question is about why we use primers in PCR. It requires two reasons. I know only one reason though. It is so that DNA polymerase can attach to primer and make a copy of nucleotide from there. But i don't know what is the other reason. Another question is about why the primer bonds to 3' end of the DNA you want to copy. and explained why. I really have no clue for this one. Plzz help.