woi

I've been so frustreted these past few days because i can't find the answer for this question - why are primers consisted of ribonucleotides and not of deoxyribonucleotides? I know that the DNA polymerase can not start the replication process because they have the proofreading activity, so DNA polymerase alfa start the replication process and adds a couple of hundred ribonucleotides and after that DNA polymerase delta adds on that a couple of thousand deoxyribonucleotides and so on...But why does DNA polymerase alfa add ribonucleotides instead of deoxy? it would be much easier, no enzymes would be needed after to elimniate the primers. Please help me with this! I know that the answer must be very simple but my mind is deffinetly stuck at this point...