The genetic information of all living cells is stored in the DNA composed of the four canonical bases adenine (a), cytosine (c), guanine (g) and thymine (t).
The chemical structures that form the units of DNA and RNA and that encode genetic information i.e. the bases that make up the base-pairs are A, G, T, C and U (see DNA).
形成DNA、RNA单体以及编码遗传信息的化学结构，也就是组成碱基对的碱基包括A、G、T、C、U。
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Sequencing involves determining the order of the bases — the chemical units of DNA that are represented by the letters A, C, G and T — in a gene or on a chromosome.