So we have N number of nucleotides in the DNA molecule. Now, if we want to add one more nucleotide, we actually have to take the dNTP, the deoxy nucleotide triphosphate, and add it onto the DNA molecule in the process. What we do is we form a phosphodiather bond between this molecule and this molecule. And so what we do is we extend the DNA chain by one. And so now we have N plus one number of nucleotides. And in the process, every time we form the phosphor diastabond, we release a PP molecule where PP stands for Pyrophosphate.