What everybody knows

The journalist who wrote those words would have felt on safe ground. Everyone knows that genes are composed of words written in the genetic code and that together these make up a book, or an instruction manual, for the organism. In this information age one of the most prominent identities of the gene is as information, code, programme, blueprint, recipe, and even ‘book of life’. These metaphors dominate popular understanding of genetics and molecular biology. When the Human Genome Project determined the sequence of human DNA, the scientists were said to have decoded the book of life. The efforts that followed to understand the functions of the many new and unexpected structures found in the genome and which we described in previous chapters are apparently decoding the book of life a second time. If scientists identify loci relevant to an illness, they have cracked the code for that disease. When someone sequences those loci, they too will have cracked the code, or perhaps deciphered the message, and the scientists who work out some of the interactions between molecules that connect activity at that locus to the disease will probably be congratulated on cracking the code for a third time. It is easy to dismiss such clichéd and thoughtless use of information language. However, many scientists are attached to the view that genes are, ultimately, units of information. They see this as a profound insight into the nature of living systems, and as one of the most important ‘big picture’ conclusions to have emerged from genetics and molecular biology.