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DNA is a long polymer comprising a deoxyribose and a phosphate backbone having four bases: thymine, adenine, cytosine and guanine. It is situated in the cell nucleus and in the mitochondria.

RNA is a polymer comprising ribose and a phosphate backbone with the bases uracil, cytosine, adenine and guanine. It is situated in the cytoplasm, nucleus and the ribosome.

DNA is a two stranded polymer of deoxynucleotides joined by phosphodiester linkage. The two antiparallel polynucleotide wind in a right handed manner around a common axis to create a $20\stackrel{∘}{\mathrm{A}}$diameter double helix. Each base pair comprises the same width that indicates the perfect symmetry of DNA, without considering the base composition. The A.T and G.C base pairs are interchangeable.

Double stranded RNA constitute the genetic material of some viruses, but it is synthesized as a single strand. The single strand RNA can fold back so that the complementary sequences base-pair to create double stranded stems comprising single stranded loops. The double stranded RNA cannot assume a B-DNA conformation because of the steric clashes coming in the 2’-OH groups.