recognized easily the blue colour of the cells transfected with plasmids which did not recombine with a fragment of lav dna is not modified to the contrary cells transfected by a recombinant plasmid containing a lav dna fragment yield white colonies the technique which was used is disclosed in gene 1983 26 101 this strain was transformed with the ligation mix using the hanahan method hanahan d 1983 j mol biol 166 557 cells were plated out on tryptone agarose plate with iptg and x gal in soft agarose white plaques were either picked and screened or screened directly in situ using nitrocellulose filters their dnas were hybridized with nick translated dna inserts of puc18 hindiii subclones of u03bbj9 this permitted the isolation of the plasmids or subclones of u03bb which are identified in the table hereafter in relation to this table it should also be noted that the designation of each plasmid is followed by the deposition number of a cell culture of e coli tgi containing the corresponding plasmid at the u201c collection nationale des cultures de micro organismes u201d c n c m of the pasteur institute in paris france a non transformed tgi cell line was also deposited at the c n c m under nr i 364 all these deposits took place on nov 15 1984 the sizes of the corresponding inserts derived from the lav genome have also been indicated positively hybridizing m13 phage plates were grown up for 5 hours and the single stranded dnas were extracted m13mp8 subclones of u03bbj19 dnas were sequenced according to the dideoxy method and technology devised by sanger et al sanger et al 1977 proc natl acad sci usa 74 5463 and.