2Genetic Information

We started out with a view of information in the form that is most intuitive and most familiar to us, that is information in human communication. This notion of information involves a sender and a receiver, as well as a supporting code or language. We saw that this notion could easily be extended to animal communication. Can we go further, and speak of information, language and code in connection with biology in general? Of course we can. A domain of biology in which information plays a leading role, and which deserves a close study in its own right, is genetics. How this field is related to information, language, code and the specific features of that relationship are issues that we will consider in the following.

2.1. A central concept in biology

Molecular biology devotes particular attention to information that is transmitted from generation to generation. The message of heredity is generally carried by an element of DNA. DNA is a linear chain consisting of pairs of nucleotides. The four nucleotides that constitute DNA are designated by the letters A, T, G and C, which stand for the corresponding molecules that are the chemical bases: adenine, thymine, guanine and cytosine. However, DNA does not resemble a string of pearls, in which each base would be one of four possible bases. Instead, it is more like a ladder (see Figure 1.1), in which each rung is a pair of nucleotides. This happens because of the affinities that exist between A and T, and between ...

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