What is the structure of DNA?

DNA has a double-helix structure that closely resembles a twisted ladder. 

A DNA molecule is made up of two DNA strands that are made of alternating phosphate and sugar (deoxyribose) molecules and held together by the hydrogen bond present between the two complementary bases. The two strands run in opposite directions and are helically twisted around the same axis, forming a right-handed double helix. A single turn is made up of 10.5 nucleotides and the distance between each turn is 3.6 nm.