THE MECCANO OF LIFE The Genetic Code Carl R . Woese (Harper and Row, New York, Evanston, and London, 1967 ; 200 pp., 8816. Paper ed. 561-)

The genetic code is the system by which genetic information is coded in the DNA molecules by the sequential arrangement in triplets of four chemical substances, the bases adenine, guanine, cystosine and uracil. Triplets formed by combinations of three of these bases are the basic units of genetic information ; the gene is a string of such triplets. Each triplet specifies an amino-acid and a complex intracellular mechanism incorporates these into polypeptides. All of the basic substances have been produced experimentally from mixtures of simple gases likely to have been present in the primeval atmosphere of the earth in what is called the prebiotic period.

The author has made an excellent survey of all this in exactly 200 pages. There is a clear account of the early theoretical approaches that followed the Watson-Crick model for the DNA molecule and preceded the development of an in vitro protein synthesizing system by Nirenberg and Matthaei in 1961. The modern experimental techniques used to elucidate the code are discussed in detail. The processes of transcription and translation are particularly well described, the relatively new concept of tape-reading being used to clarify these complex processes.

This book is not light reading. I t is an excellent textbook for the student of molecular biology or genetics.

Alan Grant.