So before we discuss what the backbone is let's actually discuss how the different nucleotides are actually linked together in our polymer. So, remember, just like in proteins, we have these monomers known as amino acids, linked together by these special bonds known as peptide bonds. In nucleic acids, we have these monomers, our nucleotides, linked together by special bonds known as three to five phosphol diaster bonds or phosphol diaster linkages. Okay, so what exactly is a three to five or three prime to five prime phosphol diastolinkage? So let's take a look at the following subsection of our nucleic acid. Now notice because this sugar doesn't have a hydroxyl group on that second carbon.