This can be seen in the next model. The A residues are red, T residues are red-orange, G residues are green, and C residues are cyan. Note also the positions of the phosphoryl groups which are orange and the 2'-deoxyribose molecules in gray. The backbone sugar atoms are different shades of gray. Note the antiparallel association of the two strands.
Phosphate groups give a high, uniform negative charge.
Another feature of the double helix is that the strands are held together only by H-bonds and by hydrophobic interactions between the bases. As a result if these weak interactions are disrupted by heat, acidic or basic conditions, or chaotropic agents, the DNA strands can be separated. This separation is referred to as DNA melting or denaturation. The denaturation conditions are dependent on the proportion of AT and GC base pairs, and on the sequence of the bases. Perhaps the most important feature of the double helix regarding its function is that all the information in it is redundant.