Mechanism of conjugation and recombination in bacteria. XVIII. Polarity of donor DNA strands transferred to the recipient as determined by DNA-RNA hybridization.

Polarity of donor DNA strand transferred into recipient during conjugation in Escherichia coli K-12 was determined by DNA-3H-RNA hybridization. Lambda prophage was used as a marker. The defective lysogen Hfr H (lambdat11) as a donor and thermosensitive F- CR34 dnaB strain as recipient were used. Two sets of hybridization experiments, with 1-strand specific lambda mRNA and lambda mRNA specific for both phage strands but with large excess of r-strand specific mRNA, were carried out. Strand 1 of lambda DNA was detected preferentially in recipient cells mated at restrictive temperature, when Hfr transferred its genophore in the order gal-lambda-bio. Thus the genophore is transferred with 5'OH at its origin.