脱氧核糖核酸DNA

生理条件下主要为 B 型 DNA：直径约 2 nm，每圈约 10.5 个碱基对，螺距约 3.4 nm。两条链的糖-磷酸骨架在外侧，碱基在内侧，A 与 T 形成两个氢键，G 与 C 形成三个氢键。碱基平面之间的堆积作用是稳定双螺旋的主要能量来源。双螺旋表面有大沟和小沟，蛋白质常通过大沟识别特定序列。

Under physiological conditions DNA is mainly B-form: about 2 nm across, with about 10.5 base pairs and 3.4 nm per turn. The sugar–phosphate backbones lie outside and the bases inside; A pairs with T by two hydrogen bonds and G with C by three. Stacking between base planes provides most of the energy that stabilises the helix. The surface has major and minor grooves, and proteins usually read specific sequences through the major groove.

1944 年艾弗里、麦克劳德和麦卡蒂证明 DNA 是肺炎球菌转化因子。1952 年赫尔希-蔡斯噬菌体实验进一步证实。1952 年富兰克林拍摄的“照片 51 号”显示了螺旋特征；1953 年沃森和克里克建立双螺旋模型，并指出碱基配对暗示了复制机制。1958 年梅塞尔森和斯塔尔证明 DNA 半保留复制。1962 年沃森、克里克和威尔金斯获诺贝尔生理学或医学奖。

In 1944 Avery, MacLeod and McCarty showed DNA is the pneumococcal transforming principle, and the Hershey–Chase phage experiment of 1952 confirmed it. Franklin's 'Photo 51' of 1952 showed the signature of a helix, and in 1953 Watson and Crick built the double-helix model, noting that base pairing suggested a copying mechanism. Meselson and Stahl demonstrated semi-conservative replication in 1958. Watson, Crick and Wilkins received the 1962 Nobel Prize in Physiology or Medicine.

加热或强碱可使双链解开（变性），260 nm 吸光度增加（增色效应）；Tm 值随 G+C 含量升高而升高，缓慢冷却可复性。人类基因组约 32 亿碱基对，2003 年人类基因组计划完成测序。DNA 指纹用于法医鉴定和亲子鉴定；DNA 也被研究作为超高密度信息存储介质和纳米结构材料（DNA 折纸）。

Heat or strong base separates the strands (denaturation), raising absorbance at 260 nm (the hyperchromic effect); the melting temperature Tm rises with G+C content, and slow cooling lets strands reanneal. The human genome has about 3.2 billion base pairs, sequenced by the Human Genome Project in 2003. DNA profiling is used in forensics and paternity testing, and DNA is being explored for ultra-dense data storage and nanostructures (DNA origami).