1. 1860s - G. Mendel described the basic principles of inheritance. 1866- E. Haeckel proposed that the nucleus contains the factors necessary for heredity. 1871- F. Miescher described some of the chemical property of DNA (C 29 H 49 N 9 P 3 O 22 ). At that time proteins were supposed to be the hereditary material. 1989 - Altmann names "nucleic acids“. 1903 - Walter Sutton proposes that chromosomes contain genetic material. 1908 – All 4 bases in DNA now characterised, (incl. T & C) in roughly equal amounts. 1909 - Enzymes found to be made from proteins. Archibold Garrod proposes chromosomes affects enzymes. 1915 - Phosphate "backbone" proposed to connect DNA bases together. 1927 - Ribose sugar associated with DNA characterised. 1928 - F. Griffith experiments with rough (R) and smooth (S) strains of Streptococcus pneumoniae in mice. 1941 - Beadle and Tatum propose "one gene, one enzyme" hypothesis. 1944 - Avery, MacLeod, McCarty show DNA is "transforming" agent (e.g., genetic material). A brief history of Genetics

2. 1952 - Alfred Hershey & Martha Chase demonstrate that DNA contains genetic material. 1953 - Postulation of a complimentary, double helical structure for DNA (by Watson and Crick). 1955 - Chargaff & Davidson publish exhaustive set of three volumes on "The Nucleic Acids", describing in great detail their physical properties and characterisation. 1956 -Genetic experiments support hypothesis that genetic messages of DNA are conveyed by its sequence of bp. 1958 - Meselson and Stahl demonstrate that DNA replicates semi- conservatively. Isolation of the first enzyme (DNA polymerase I) by A. Kornberg 1959 - Discovery of RNA polymerase. 1960 - Discovery of messenger RNA. 1961 - The triplet nature of the genetic code is discovered. Monad and Jacob propose operon model of gene regulation 1965 - Appreciation that genes conveying antibiotic resistance in bacteria are often carried on small bits of extrachromosomal DNA (plasmids). 1966 - Establishment of complete genetic code. 1967 - Isolation of the enzyme DNA ligase. 1970 - Isolation of the first restriction enzyme.

3. 1970 - Temin and Baltimore report the discovery of reverse transcriptase in retroviruses. 1972 - Use of ligase to link together restriction fragments. First recombinant molecules generated. 1973 - Eukaryotic genes are cloned in bacterial plasmids. 1976 - Retroviral oncogenes are identified as the causative agents of transformation. 1977 - DNA sequencing becomes possible. Interrupted genes are discovered and splicing of their transcripts is inferred. 1978 - Production of first human hormone (somatostatin) using recombinant DNA methods. 1979 - Cellular oncogenes are discovered by transfection. 1981 - Catalytic activity of RNA is discovered. Transgenic mice and flies are obtained by introducing new DNA into the germ line. 1983 - First version of "GenBank" created for storage of DNA sequences. 1986 - Proposal of Intramolecular Triplex structure for certain purine rich DNA sequences. 1989 - Polymerase Chain Reaction (PCR) technique first used. 1995 - First BACTERIAL genomes completely sequenced. (Haemophilus influenzae and Mycoplasma genitalium).

4. 1996 - Genome of first EUKARYOTE completely sequenced. (Saccharomyces cerevisiae, 13,000,000 bp on 16 chromosomes). 1997 - Dolly the Sheep cloned. E.coli genome sequenced. 2002/03 - Genome of Pasmodium (30 MB), Caenorhabditis elegans (100 Mb), Arabidopsis thaliana (100 Mb), Drosophila melanogaster (120 Mb), Mus musculus (300 Mb) have been completely sequenced. 2004 - The Homo sapiens genome (3000 MB) is sequenced. 2009 – Full Genome sequencing. The Genomics and Post-Genomics age.

5. The transforming principle is DNA (F. Griffith experiments, 1928) The discovery of the genetic material Streptococcus pneumoniae strains  R (rough) and S (smooth)

6. 1944 – O.T. Avery, C. MacLeod and M. McCarty experiments The DNA as transforming principle Chemical composition Prep. N. C H N P 37 34,27% 3,89% 14,21% 8,57% 42 35,50% 3,76% 15,36% 9,04% DNA 34,2% 3,2% 15,32% 9,05% I passaggi fondamentali nei protocolli attualmente disponibili sono: 1- 2-3-5-6-7-10-11

7. The mechanics of inheritance

8. 1952 - Alfred Hershey and Martha Chase experiments with T2 bacteriophage in E. coli T2 bacteriophages infecting an E.coli cell

9. 1953 - Il modello proposto da Watson e Crick per la struttura della doppia elica del DNA 1) Scoperta del DNA (Miescher, 1869). Caratterizzazione delle 4 basi azotate (1903-08). Lo scheletro che connette le basi azotate è formato da gruppi fosfato (1915). Il ribosio è associato con il DNA (1927). Le principali tappe di una grande scoperta 2) Idrolisi del DNA, A/T = 1 C/G = 1 (Esperimenti di Chargaff). James Watson and Francis Crick

10. 3) Diffrazione ai raggi X. I primi pattern di diffrazione risalgono al 1938 ma solo nel 1950 fu possibile ottenere foto di diffrazione ad alta risoluzione nel laboratorio di M. Wilkins. 2 periodicità  3,4 Å e 34 Å 4) La struttura ad  elica delle proteine (L. Pauling, 1951). 5) Elettrotitolazioni (basi legate da legami idrogeno). 6) Il legame fosfodiesterico 3’--5’ (A.L. Todd, 1952). Rosalind Franklin Maurice Wilkins