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 (C29H49N9P3O22). 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

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.

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).

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.

The transforming principle is DNA (F. Griffith experiments, 1928)

The discovery of the genetic material

Streptococcus pneumoniae strains R (rough) and S (smooth)

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

The mechanics of inheritance

1952 - Alfred Hershey and Martha Chase experiments with T2 bacteriophage in E. coli

T2 bacteriophages infecting an E.coli cell

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

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 FranklinMaurice Wilkins