How are HFR strains formed?

By: Adrian BompaUpdated: April 23, 2021


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    June 26, 2022
All Hfr strains arise from the integration of a conjugative plasmid into the bacterial chromosome by one of several possible types of recombination events. The most commonly used Hfr strains have been formed by either spontaneous or UV-induced integration of the E. coli F factor (see chapter 126).

So, what is the difference between F+ and HFR?

Hfr cells can become F+, but F+ cells cannot become Hfr. The fertility plasmid is integrated into the host cell chromosomal DNA in Hfr cells while the fertility plasmid is independent in F+ cells. Hfr cells are able to convert F- recipient cells to F+, but F+ cells are not able to convert F- recipient cells to F+.

Likewise, how does an HFR strain of E coli transfers chromosomal DNA to an F strain?

Such a donor strain is called a high frequency of recombination (HFr) strain. The donor DNA is integrated into the recipient cell's DNA by homologous recombination. The recipient now carries transferred genes, but remain F- where as donor cell remains HFr.

What is the end result of HFR bacterial conjugation?

If the Hfr cell loses the F-plasmid sequence, it reverts to a F–state. The end result of the conjugation process is similar to that obtained in sexual reproduction in eukaryotes (see below), namely the original F–cell now has a genome derived in part from itself and from the “donor” Hfr strain cell.

How much time is required to inject a copy of the whole HFR E coli?

about 100 min


What is f prime plasmid?

F' (F-prime) bacteria are formed by incorrect excision from the chromosome, resulting in F plasmid carrying bacterial sequences that are next to where the F episome has been inserted. F bacteria do not contain F factor and act as the recipients.

When F+ cells are mixed with F − cells eventually all the cells will become F+?

Therefore plasmids may have been important in spreading genes for important cellular functions across many different groups of bacteria. Contact is required between an F+ and an F- cell for conjugation to occur. When F+ cells are mixed with F- cells, eventually all the cells will become F+.

What is af plasmid?

The F plasmid is an example of a large plasmid, which contains genes that allow the plasmids DNA to be transferred between cells. It is found in the bacterium E. This joining via a pilus in order to transfer DNA between bacteria is known as conjugation. Therefore the F plasmid is known as a conjugative plasmid.

What is an HFR cell quizlet?

Hfr cell is an F+ cell, where the F factor is integrated in the chromosome (plasmid becomes a episome) You just studied 7 terms!

How many DNA molecules are transferred after each transformation?

How many DNA molecules are transferred after each transformation? Explanation: Each transformation results from the transfer of a single DNA molecule of double-stranded DNA. 7. Which of the following enzymes acts on the DNA after its entry into the cell?

What are the types of conjugation?

What are the different types of bacterial conjugation? - Quora. F+ conjugation: This results in the transfer of an F+ plasmid (coding only for a sex pilus) but not chromosomal DNA from a male donor bacterium to a female recipient bacterium.

What is interrupted mating experiment?

interrupted mating. A technique used to MAP bacterial genes by determining the sequence in which donor genes enter recipient Cells. A gene MAPping technique in which bacterial conjugation is disrupted after specified time intervals.

Are all bacteria naturally competent?

Many bacteria are naturally competent, able to actively transport environmental DNA fragments across their cell envelope and into their cytoplasm.

What DNA is transferred from an HFR donor cell to an F recipient cell?

coli DNA (more) Now, during conjugation between an Hfr cell and a F cell a part of the chromosome is transferred with F.

What is the F factor in bacteria?

sex factor
Also called F factor, fertility factor. a plasmid in certain bacteria that enables transfer of genetic material from a donor cell to a recipient by conjugation, resulting in recombination.

What is the result of conjugation between F and F cells?

When conjugation occurs, the F+ cells can act as F donors. The recipient cell becomes converted into F+, because it now contains a circular F genome. The transfer of the F plasmid from F+ to F is rapid, so the F plasmid can spread like wildfire throughout a population from strain to strain.

How does homologous recombination work?

Homologous recombination is a type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may be also RNA in viruses).

What determines how much of the chromosomal DNA is transferred?

The amount of chromosomal DNA that is transferred depends on how long the two bacteria remain attached by the conjugation bridge. In order to mobilize chromosomal DNA, the plasmid must first integrate into the chromosome. Hfr strains were used in earlier times to identify the order of genes on the E.

Is transduction horizontal gene transfer?

Horizontal gene transfer may occur via three main mechanisms: transformation, transduction or conjugation. Transformation involves uptake of short fragments of naked DNA by naturally transformable bacteria. Transduction involves transfer of DNA from one bacterium into another via bacteriophages.

Which of the following can be used as a measure to construct a linkage map of the HFR chromosome?

10. Which of the following can be used as a measure to construct a linkage map of the Hfr chromosome? Explanation: Each gene enters the F cell at a characteristic time, and a linkage map of the Hfr chromosome can be constructed using time of entry as a measure.