High-Frequency Recombination (Hfr) Strains: Mechanism of Transfer

Introduction

High-frequency recombination (Hfr) strains are bacterial cells that possess a conjugative plasmid that has integrated into the bacterial chromosome. This integration allows the transfer of chromosomal DNA from the Hfr cell to a recipient cell during conjugation.

Mechanism of Transfer

The mechanism of transfer in Hfr strains involves the following steps:

1. Formation of a conjugation bridge: The Hfr cell produces a sex pilus that attaches to a recipient cell.
2. Transfer of chromosomal DNA: The conjugative plasmid, along with the attached chromosomal DNA, is transferred through the sex pilus.
3. Reconstitution of the recipient DNA: The recipient cell integrates the transferred chromosomal DNA into its own chromosome through homologous recombination.

Difference between F and Hfr Cells

F cells possess a self-transmissible F plasmid, while Hfr cells have a conjugative plasmid that is integrated into the bacterial chromosome. As a result, F cells can transfer the F plasmid, while Hfr cells can transfer chromosomal DNA.

Quizlet Flashcards

• Term: How does an F cell differ from an Hfr cell? Definition: F cells possess a self-transmissible F plasmid, while Hfr cells have a conjugative plasmid integrated into the bacterial chromosome.

Conclusion

Hfr strains are important in genetic research as they allow for the transfer and mapping of genes. By understanding the mechanism of transfer in Hfr strains, scientists can gain valuable insights into the molecular processes involved in bacterial conjugation.