DNA Structure

Deoxyribonucleic acid (DNA) is a polymer of nucleotides that provides the chemical basis for inheritable characteristics of all cellular organisms. The genetic information in DNA is defined by the sequence of individual bases, which are the pyrimidines, cytosine and thymine and the purines, guanine and adenine. Hydrogen bonds form between appropriately positioned donors and acceptors on the bases of each strand, such that A pairs with T and G pairs with C. In the cell, DNA usually adopts a double- stranded helical form, with complementary base pairing holding the two strands together. The most stable double-stranded conformation is called B-form DNA. A high degree of flexibility in DNA molecules means that a wide range of other structures can occur under specific conditions, including some that involve more than two strands of DNA.