Hfr cell
From Free net encyclopedia
A hfr cell (also called hfr strain) is a bacterium with a conjugative plasmid (often F) integrated into its genomic DNA. Hfr is the abbreviation for high frequency recombination. Unlike a normal F+ cell, hfr strains will, upon conjugation with a F- cell, attempt to transfer their entire DNA through the pilus to the F- cell. As fragile a structure as a pilus will, however, likely break, and so the transfer is rarely complete. Thus, the F- cell uses only part of the genomic DNA of the F+ cell for recombination. Though there is some debate on the issue, the pili themselves do not seem to be the structures through which the actual exchange of DNA takes place; rather, some proteins seem to open a channel between the bacteria.