Electron microscope heteroduplex studies of sequence relations among plasmids of Escherichia coli: I. Structure of F-prime factors

摘要: Abstract The sequence relations between some bacterial F-prime factors in Escherichia coli have been determined by observing, the electron microscope, pattern of duplex and single-stranded regions heteroduplexes consisting one strand from episome complementary another. All F-primes studied a short piece F missing. They appear to formed excision their respective Hfr's type I process (Scaife, 1967), leaving remaining chromosome. missing is same lac close relatives F450 1s , although former was derived Hfr2 latter two Hfr3. Thus, there evidence for hot spots on insertion at different places K12 chromosome give F-primes. However, 8 . physical structure number episomes has studied. In particular, we genetic structures set deleted episomes, prepared P1 kc transduction original mostly transfer genes. various markers physically mapped. A general model proposed.