stopping the conjugation at the appointed time (intervals) developed by
Wollman and Jacob provided the possibility for mapping the genes and
constructing of genetic map of E. coli was made, whose circilar DNA
molecule is divided into 90 equal segments (minutes) — Figure 2–13. Such
maps have been made also for other biological objects.
Figure 2–13. Genetic map of Escherichia coli made upon scale. The map is divided into 90 intervals of one minute each. The symbols and the description of the different genetic markers are given in Appendix 1 (After Taylor and Thoman, 1964; Taylor, 1970).
In 1951 Lederberg and co-authors have discovered in Salmonella
typhimurium a transfer of genetic material by viruses leading to
recombination that have been earlier observed in E. coli K-12 (Lederberg,
Tatum, 1946 a, b; Tatum, Lederberg, 1947). This process was given the