Glossary

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Bases

Building blocks of the nucleic acids DNA and RNA

Four bases are present in DNA: adenine (A), cytosine (C), guanine (G) and thymine (T). In RNA, thymine is replaced by uracil (U).

These four bases encode the genetic information; thus, the four letters A, C, G and T are sometimes called “the alphabet of life”.

DNA can be visualised as a coiled ladder, the rungs of which are composed of pairs of bases; adenine always pairs with thymine, and cytosine always with guanine. A group of three bases of DNA can be recognised as a group (“codon”) specifying a particular amino acid. Hence, the sequence of codons in DNA determines the sequence of the chain of amino acids in a protein.