Now if the backbone is found on the exterior, then the interior, the inside of that double helix essentially contains the nitrogenous bases. So if we examine on the inside portion of our molecule, we have these nitrogenous bases, which are relatively non polar, while on the outside we have the actual strand, we have the backbone that contains the sugar and phosphate groups, and these are found on the outside. Point number three. These bases are essentially perpendicular with respect to the common axis. So, once again, if this is the common axis, then these bases are essentially like so if this is the common axis, the bases are at a 90 degree angle with respect to this common axis. And this allows for the stacking of the bases on top of one another.