From a biologist’s point of view, the 20th century can be named the ‘century of
genetics’: starting with the rediscovery of the Mendelian laws by Carl Erich
2 F. HammarCorrens (Berlin), Erich von Tschermak (Vienna) and Hugo de Vries
(Amsterdam) in 1900 [1]. Mendel’s rules, originally formulated in 1866, postu￾late that different genetic traits are inherited independently. In 1902 Walter
Stanborough Sutton observed chromosomal movements during meiosis and de￾veloped the chromosomal theory of heredity. He stated that the chromosomes
are the carriers of Mendel’s ‘factors’ of heredity. Sutton gave these factors the
name we still use today: he called them ‘genes’. In 1903 Sutton and Theodor
Boveri working independently suggested that each germ cell contains only one
half of each chromosome pair. In 1905, Edmund Wilson and Nellie Stevens pro￾posed the idea that separate X and Y chromosomes determine sex. Thomas Hunt
Morgan started experiments with the fruit fly Drosophila melanogaster in 1910
and proved that certain genes are linked to each other and that linked genes can
be exchanged by a mechanism called crossing over [2, 3]. Based on these results,
Alfred Sturtevant was able to draft the first genetic maps to locate the genes on
the chromosomes in 1913 [4]. Herman Müller, who also worked in Morgan’s lab￾oratory, performed the first experiments to produce mutations by radioactive
radiation. In 1927 he was able to demonstrate that X-rays cause a high rate of
mutations [5]. These experiments, A. E. Garrod’s observation of inherited dis￾eases like phenylketonuria [6] and later the work of George Beadle and Edward
Tatum on the fungus Neurospora crassa, showed the relationship between genes
and enzymes and led to the formulation of the ‘one-gene-one-enzyme’ hypo￾thesis in 1941 [7, 8].