DNA, or deoxyribonucleic acid, is one of the two key molecules responsible for encoding genetic information, with the other being RNA. In humans, DNA serves as the primary genetic material, from which RNA is transcribed. In certain other organisms, RNA takes on the role of genetic material, with DNA being transcribed from it in reverse. DNA is characterized as a double-stranded molecule, linked by weak hydrogen bonds between nucleotide base pairs. Its structure forms a double helix, resembling a long ladder twisted into a coil. The ladder's sides are made up of a backbone consisting of sugar and phosphate molecules, while the "rungs" are composed of nucleotide bases, weakly bonded in the center by hydrogen bonds.There are four nucleotides in DNA, each with a specific base: adenine (A), guanine (G), cytosine (C), and thymine (T). Base pairing occurs naturally between A and T, and G and C, allowing the sequence of one DNA strand to be easily inferred from its complementary strand.The genetic code within DNA is organized into triplets, such as ATG, with the corresponding sequence on the partner strand being TAC. The first conclusive evidence that DNA carries genetic information was presented in 1944 by Oswald Avery, Maclyn McCarty, and Colin MacLeod. The iconic double helix structure of DNA was unveiled in 1953 by James D. Watson and Francis H.C. Crick, with crucial contributions from crystallographer Rosalind Franklin. In 1962, Watson and Crick, along with Maurice H.F. Wilkins, were awarded the Nobel Prize in Physiology or Medicine for their discoveries.For further reading, see: DNA (figurative); and the Transforming principle.