在所有生物体中构成基本遗传物质的化合物。从结构上讲，DNA是由两条链相互缠绕构成弹簧状结构称为双螺旋。每条链的主干是由脱氧核糖分子连接磷酸残基形成，连在主干上的是称为碱基的化学结构，它们从主干伸向螺旋结构的中央，有4种类型---腺嘌呤、胞嘧啶、鸟嘌呤和胸腺嘧啶（表示为A、C、G、T）。在DNA中C只能和G通过氢键连接，A只能和T连接，通过所谓氢键发生的这些作用将两条链连在一起。每条DNA链的主干上都有一系列G、A、T、C。正是这些碱基序列构成密码并被细胞翻译成一个新的蛋白。另一条链（互补链或反义链）的序列总是与第一条链相匹配，即C与G，A与T，反过来也一样。

The chemical that forms the basis of the genetic material in virtually all living organisms. Structurally, DNA is composed of two strands that intertwine to form a spring-like structure called the double helix. Each strand is formed by a backbone of deoxyribose sugar molecules linked by phosphate residues. Attached to each backbone are chemical structures called bases, which protrude away from the backbone towards the center of the helix, and which come in four types - Adenine, Cytosine, Guanine, and Thymine (designated A, C, G and T). In DNA a C can only hydrogen-bond with a G, and an A only with a T, these interactions, formed by so called hydrogen bonds, hold the two strands together. Each strand of DNA has a series of Gs, As, Ts and Cs attached to its backbone. It is the sequence of these bases that forms the code which is translated by cellular machinery to create a new protein. The other (complementary or antisense) strand always has a sequence that matches the first strand, with each C complemented by a G, and each A by a T, and vice versa.