OCR GCSE Biology B · J257
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: Coding for ProteinsDNA contains four different bases: adenine, thymine, cytosine and guanine. Their names are represented by the letters A, T, C and G. These letters are a model of the genetic code: it is the order of the bases, rather than the shapes of the letters themselves, that carries information.