Sage-Tips

What is the significance of Hfr cells?

A bacterial cell that possesses the F factor integrated into the bacterial genome, hence, when it conjugates with another bacterium, it attempts to transfer a copy of the F factor as well as a portion of or the entire chromosome to the recipient bacterium.

How do Hfr bacterial strains differ from other bacteria?

The key difference between F+ strains and Hfr is that F+ strains have F plasmids in the cytoplasm freely without integrating into bacterial chromosomes while Hfr strains have F plasmids integrated to their chromosomes.

What can Hfr strains of bacteria be used for?

When the F factor is integrated into the bacterial chromosome, it can still act as the donor in a conjugation cross. These integrated strains are called Hfr, because of the high frequency of recombination that occurs when mated with F- bacteria. In 1957, these Hfr strains were used to map the bacterial chromosome.

Why Hfr is high frequency of recombination?

After the cross between Hfr cell and F- cell, recipient cell remains recipient. In this conjugation, chromosomal DNA is always almost transfer from donor to recipient cell together with portion of F- factor. So, frequency of recombination is high.

What is Hfr in microbiology?

A high-frequency recombination cell (Hfr cell) (also called an Hfr strain) is a bacterium with a conjugative plasmid (for example, the F-factor) integrated into its chromosomal DNA. The integration of the plasmid into the cell’s chromosome is through homologous recombination.

What is an Hfr cell quizlet?

Hfr cells (high frequency recombination) have the F plasmid incorporated INTO THE CHROMOSOME! Crossing over takes place between F factor and chromosome. Bacterial genes may be transferred from an Hfr cell to an F- cell in conjugation. In conjugation, F is nicked and the 5′ end moves into the 5- cell.

What is Hfr in bacterial conjugation?

In the process of conjugation, we can distinguish between two types of bacterial cells (of the same species). These are known as a Hfr (high frequency recombination) cells. This plasmid contains the genes needed to transfer a copy of its DNA into a cell that lacks an F-plasmid, a so called F–cell.

What is an HFR cell quizlet?

What must be present on the primary chromosome for the cell to be Hfr?

F+ denotes cells that contain the F plasmid, while F− cells do not. The F plasmid is considered to be an episome which may become integrated into the main chromosome. When the F genes become integrated into the chromosome, the cell is said to be Hfr (high frequency of recombination).

What happens when a bacteriophage carrying bacterial DNA infects a new bacterium?

Transduction occurs when a bacteriophage containing bacterial DNA infects a recipient bacterium and transfers this bacterial DNA to the recipient bacterial host cell. This transferred bacterial DNA may then be incorporated into the genome of the recipient bacterium.

What does Hfr mean in genetics?

High frequency of recombination. A strain of bacteria that has incorporated an F factor into its chromosome and can then transfer the chromosome during conjugation.

Why is Lysogeny advantageous to a bacteriophage?

The lysogenic cycle allows a phage to reproduce without killing its host. Some phages can only use the lytic cycle, but the phage we are following, lambda ( λ), can switch between the two cycles.

What is high frequency recombination (HFR) bacteria?

When F-plasmid (sex factor) integrated with chromosomal DNA then such bacteria is known as high frequency recombination (Hfr) bacteria. In the cross (conjugation) between Hfr cell and F- cell, frequency of recombination is very high but frequency of transfer of whole F-factor is very low. Hfr cell acts as donor while F- cell acts as recipient.

Why are Hfr cells called Hfr cells?

Therefore the recipient cells now have got three different types of DNA – its own chromosomal DNA, some part of F plasmid along with some part of donor’s chromosomal DNA. So because crossing with Hfr cells results in high degree of recombination in recipient cells such cells are called Hfr cells.

Why do molecular biologists use Hfr strain of bacteria?

Such Hfr strains are very useful in studying gene linkage and recombination. Hence, molecular biologists and geneticists use Hfr strain of bacteria (often E. coli) to study genetic linkage and map the chromosome.

Can Hfr cells do conjugative transfer?

An Hfr cell can transfer a portion of the bacterial genome. Despite being integrated into the chromosomal DNA of the bacteria, the F factor of Hfr cells can still initiate conjugative transfer, without being excised from the bacterial chromosome first.