What is the difference between an f and an hfr bacterial strain

This fertility factor contains the genes require for the transfer or conjugation. F — cells are the cells without F plasmid. They are designated as F — simply because they do not have F plasmid.

Figure 2. F — Cells. We just talked about F plasmid. This F plasmid is an episome which means it can either exist as an independent unit or it can integrate itself into chromosomal DNA. This integration is possible because F plasmid also contains the insertion sequence and via homologous recombination it can integrate itself. Why are they called Hfr? So because crossing with Hfr cells results in high degree of recombination in recipient cells such cells are called Hfr cells.

They are capable of forming sex pili and transferring plasmids into other bacteria which receive them. F plasmid is free in the cytoplasm. Sometimes, F plasmid integrates into the bacterial chromosome and produce recombinant DNA. Bacteria which possess F plasmid integrated into their chromosomes are known as high frequency recombinant strains or Hfr strains.

Overview and Key Difference 2. What are HFR Strains 4. Some bacterial strains possess F plasmids in addition to their chromosomes. They act as donor cells or males in bacterial conjugation. Bacterial conjugation is a sexual reproduction mechanism shown by bacteria which facilitates horizontal gene transferring between bacteria.

F plasmids can replicate independently and contain fertility factor coding genes. Hence these extrachromosomal DNA plasmids are named F plasmids due to the F factor or fertility factor. Fertility factor coding genes are essential for transfer or conjugation.

Sex pilus facilitates the cell to cell communication and contact by forming a conjugation tube. The copied F plasmid is transferred to the F- strain via conjugation tube. Once it transfers, conjugation tube dissociates. Bacterial strains which have F plasmid integrated into the chromosomes are called high-frequency recombination strains or Hfr strains. In Hfr strains, F plasmid does not exist freely in the cytoplasm.

F plasmid combines with bacterial chromosome and exists as one unit. Since Hfr strain has F plasmid or fertility factor it can act as a donor or male bacterium in bacterial conjugation. Some parts of bacterial chromosome or the entire chromosome can also be copied and transferred to the recipient bacterium when Hfr strain is involved is conjugation.

Such Hfr strains are very useful in studying gene linkage and recombination. Hence, molecular biologists and geneticists use Hfr strain of bacteria often E. High-frequency recombination occurs when a recipient bacterium receives three types of DNA after mating with Hfr strain through bacterial conjugation.