The restriction endonuclease EcoRI dependent recombination of compatible 
plasmids has been studied in RecA cells of Escherichia coli. Plasmid RP4 and the 
isogenic ColE1 type plasmids pSA14 or pSA25, differing in 
restriction-modification RM EcoRI genes, have been used to study this type of 
recombination. EcoRI dependent recombination of plasmids is demonstrated in RecA 
cells and, thus, is independent of general system of homologous recombination. 
The classes of recombinant plasmids isolated from RecA cells differ from the 
classes isolated from wild type cells. Levels of tetracycline resistance 
conferred by plasmid RP4 are shown to be dependent on the alleles of RecA+ gene, 
being extremely low in RecA cells. This property is demonstrated to be useful 
for obtaining the multicopy recombinant plasmids resulting from EcoRI dependent 
recombination in RecA cells of Escherichia coli.