DNA structure

DNA is composed of two strands of polymer, each having a phosphodeoxyribose (sugar phosphate) backbone with central nucleotide chains that are held together by noncovalent hydrogen bonds between a purine-pyrimidine pair (either adenine with thymine or guanine with cytosine), referred to as "base pairing." The energy of the hydrogen bonds is low enough to enable localized strand separation (eg, during DNA replication). Refer to UpToDate for details of DNA regulation and function.