Hfr recombination begins when an F+ plasmid with tra genes coding for mating pair formation inserts or integrates into the nucleoid to form an Hfr bacterium. A nuclease then breaks one strand of the donor's DNA at the origin of transfer (oriT) location of the inserted F+ plasmid and the nicked strand of the donor DNA begins to enter the recipient bacterium. The remaining non-nicked DNA strand remains in the donor and makes a complementary copy of itself. The bacterial connection usually breaks before the transfer of the entire chromosome is completed so the remainder of the F+ plasmid seldom enters the recipient. As a result, there is a transfer of some chromosomal DNA, which may be exchanged for a piece of the recipient's DNA through homologous recombination, but not the ability to form a conjugation pilus and mating pairs.