phosphodiester bonds are covalent bonds
that are stronger
than the hydrogen bonds
between the bases.
The 2 strands have antiparallel sugar-phosphate backbones, connected by
rungs of nitrogenous base pairs, of which there are 10 per turn.
These phosphodiester bonds are covalent bonds
that are stronger
than the hydrogen bonds
between the bases.
On the inside, the nitrogenous bases are joined by hydrogen bonds:
2 hydrogen bonds between A-T pairs,
and
3 hydrogen bonds between G-C pairs.