And remember, DNA polymerase reads from three to five and it builds from five to three. And that's why this is the end that we actually want to build the DNA primer for. So we add the DNA polymerase and we also add the four types of deoxy nucleus diet triphosphate. So we add dATP dGTP dCTP and TTP. And finally, the important component in the standard died oxy method is a tiny amount of one of the four types of Ddntp molecules. Remember, we have four different types that can exist and that's because we have four different types of bases.