The phosphate group has a negative charge which spreads the DNA out into linear formation. Nucleotides are joined by linking the phosphate on the 5' end of the deoxyribose of the second one to the 3' position of the first. One way to depict this is by a graphic of staggered linked nucleotides. The two strands of DNA run antiparallel, each base binds with its complementary base on the opposite strand. There is a major groove and a minor groove in the DNA double helix.
Regulatory proteins can often fit into the major groove.
DNA conventions I. DNA is a right-handed helix. The strands are complementary due to base pairing. This forces a compensatory twist at the higher structural level.