1. R. Olby (1974) The Path to the Double Helix, Macmillan, London — includes a particularly good account of the protein theory of the gene and its eventual overthrow.
2. P. A. Levene (1921) On the structure of thymus nucleic acid and on its possible bearing on the structure of plant nucleic acid. Journal of Biological Chemistry, 48, 119–25 — an early description of the incorrect, non-variable structure for DNA.
3. O. T. Avery, C. M. MacLeod and M. McCarty (1944) Studies on the chemical nature of the substance inducing transformation of pneumococcal types. Journal of Experimental Medicine, 79, 137–158; A. D. Hershey and M. Chase (1952) Independent functions of viral protein and nucleic acid in growth of bacteriophage. Journal of General Physiology, 36, 39–56 — the two important papers that demonstrated that genes are made of DNA. Both are reprinted in J. H. Taylor, ed. (1965) Selected Papers in Molecular Genetics, Academic Press, New York.
4. M. McCarty (1980) Reminiscences of the early days of transformation. Annual Review of Genetics, 14, 1–15; M. McCarty (1985) The Transforming Principle: Discovering that Genes are made of DNA, Norton, London — two personal accounts.