DNA structure. Because of its structural properties, DNA is well suited for long-term information storage. Genomic DNA almost always consists of two complementary strands of deoxyribonucleic acid. Each strand has a backbone consisting of deoxyribose residues connected by phosphate groups, and a base is attached to each ribose. Strand complementarity is enforced by specific interactions between the bases in each strand. The interactions create base pairs. (a) The G ≡ C and A = T base pairs are similarly sized, giving the DNA double helix a uniform width and allowing base pairs, in any sequence, to stack. Complementary base pairing facilitates replication and transmission from one generation to the next. (b) The double-helical structure and base stacking confer stability. Major and minor helical grooves in the structure provide access to genetic information for a wide range of DNA-binding proteins. The uniform structure of the DNA backbone allows the synthesis of very long polymers.