HFR Cells and Gene Transfer Notes

HFR Cells and Gene Transfer

Formation of HFR Cells

• The F plasmid can integrate into the host cell's genome.
• When this integration occurs, the host cell is termed HFR, which stands for high frequency of recombination.
• HFR cells can transfer some of their host genes to recipient cells.

Mechanism of Gene Transfer

• The sex pilus makes contact with the recipient F- cell, pulling the cells together.
• Donor chromosomes are transferred as single-stranded DNA, starting at the origin of transfer.
• Gene one, located closest to the origin of transfer, is transferred first.
• Segments of the integrated plasmid are at the beginning and end of the DNA being transferred.

Potential for Complete Genome Transfer

• It is theoretically possible for the entire genome and the F plasmid to be transferred to the recipient cell.
• However, this complete transfer does not occur because the donor and recipient cells separate before the process is finished.

Outcome of Gene Transfer

• The transferred single-stranded DNA becomes double-stranded in the recipient cell.
• Donor DNA integrates into the recipient cell's DNA via homologous recombination.
• The recipient cell acquires transferred genes but remains F-, while the donor cell remains HFR.