Strand-specific transfer of donor DNA during conjugation in E. coli.

After conjugation of E. coli, only the preformed donor DNA strand with a leading 5' end can be recovered from the recipient. DNA that was transferred to recipients from radioactive-labeled donor strains lysogenic for lambda bacteriophage was recovered as radioactive material in mature phage particles. The radioactivity was recovered in strand l when gene transfer was in the order gal-lambda-bio, and in strand r when the order of transfer was bio-lambda-gal. The assignment of the 5' end as the origin of the transferred strand follows directly from the known orientation of prophage lambda in the chromosome.