DNA is made up of structural elements called nucleotides. Their nitrogen bases are the basic structural units of nucleic acids. There are four bases in DNA – adenine, thymine, guanine, and cytosine. They are denoted by their Latin initials – A, T, G, C.
Nucleobases are involved in defining the genetic code. In the three-dimensional models below the colours of atoms are: carbon – black, nitrogen – blue, oxygen – red and hydrogen – white.
◄ Adenine Adenine (C5H5N5) takes part in cell breathing and protein synthesis. In the DNA it always bonds with thymine (C5H6N2O2). Thymine ► |
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◄ Guanine Guanine (C5H5N5O) is the third nucleobase in DNA and it bonds with citosine (C4H5N3O), which is a co-factor and takes part in phosphate transfer. Citosine ► |