So we need the DNA primer basically for that DNA polymerase to actually work. Because remember, the DNA polymerase will only initiate replication if the primer is present. And what that means is we have to know what this initial sequence is on that DNA molecule. Because to build the DNA primer, we have to know what the complementary sequence is to this group here. So if this is ACG, then we have to build a primer that contains a sequence TGC. And so we can build that in a laboratory.