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A brief history of Genetics
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).
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 semiconservatively.
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 discovery of the genetic material
The transforming principle is DNA (F.
Griffith experiments, 1928)
Streptococcus pneumoniae strains  R (rough) and S (smooth)
1944 – O.T. Avery, C. MacLeod and M. McCarty experiments
The DNA as transforming principle
I passaggi
fondamentali nei
protocolli
attualmente
disponibili sono: 12-3-5-6-7-10-11
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%
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
Le principali tappe di una grande
scoperta
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).
James Watson and Francis Crick
2) Idrolisi del DNA, A/T = 1
C/G = 1 (Esperimenti di Chargaff).
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.
Maurice Wilkins
Rosalind Franklin
2 periodicità  3,4 Å e 34 Å
4) La struttura ad a elica delle proteine
(L. Pauling, 1951).
5) Elettrotitolazioni (basi legate da
legami idrogeno).
6) Il legame fosfodiesterico 3’--5’
(A.L. Todd, 1952).