So these bonds here are basically the hydrogen bonds that hold our bases together. So what holds this entire double helix in DNA are the hydrogen bonds as well as Van der Vall forces and the hydrophobic effect. So in the inside portion of our DNA we have these hydrophobic regions. And on the outside portion, because these phosphate groups essentially point on the outside and they contain charge the exterior of the DNA of the double helix is negatively charged and it is hydrophilic while the interior is hydrophobic because it consists of these nonpolar nitrogenous bases. So DNA exists predominantly as a double helix. And what that means is we have these two strands of DNA that essentially run an antiparallel direction and they interact via different types of non covalent interactions.