Now, why do we need a template molecule? Well, we need the DNA template to basically copy that genetic information. And it's the template, that DNA template that is used to basically bring those complementary bases to that elongated polynucleotide chain. So although single stranded DNA molecules work, double stranded DNA molecules are more effective and more common as templates. So RNA polymerase uses this DNA template to basically build a polynucleotide chain that contains complementary bases as we'll see in just a moment. And finally, inside the RNA polymerase molecule at the center there is a pocket that can fit a divalent metal atom.