In the Beginning was Information

code with four different letters is employed; these four letters arearranged in “words” of three letters each to uniquely identify anamino acid. Our next endeavour is to determine whether this systemis optimal or not.The storage medium is the DNA molecule (deoxyribonucleic acid)which resembles a double helix as illustrated in Figure 17. A DNAfibre is only about two millionths of a millimetre thick, so that it isbarely visible with an electron microscope. The chemical letters A,G, T, and C are located on this information tape, and the amount ofinformation is so immense in the case of human DNA that it wouldstretch from the North Pole to the equator if it was typed on paper,using standard letter sizes. The DNA is structured in such a waythat it can be replicated every time a cell divides in two. Each ofthe two daughter cells have to have identically the same geneticinformation after the division and copying processes. This replicationis so precise, that it can be compared to 280 clerks copying theentire Bible sequentially each one from the previous one, with atmost one single letter being transposed erroneously in the entirecopying process.When a DNA string is replicated, the double strand is unwound,and at the same time a complementary strand is constructed oneach separate one, so that, eventually, there are two new doublestrands identical to the original one. As can be seen in Figure 17, Ais complementary to T, and C to G.One cell division lasts from 20 to 80 minutes, and during this timethe entire molecular library, equivalent to one thousand books, iscopied correctly.90