Hfr cell: Difference between revisions

Latest revision as of 10:52, 15 February 2025

Hfr Cell[edit]

An Hfr cell (High frequency of recombination) is a bacterium with a conjugative plasmid integrated into its chromosomal DNA. This integration allows the bacterium to transfer part of its chromosomal DNA to a recipient cell during bacterial conjugation. The process of Hfr formation and the subsequent genetic exchange play a crucial role in bacterial genetics and the study of gene mapping.

Formation of Hfr Cells[edit]

Hfr cells are formed when an F plasmid (fertility plasmid) integrates into the bacterial chromosome through a process called homologous recombination. This integration occurs at specific sites on the chromosome, known as insertion sequences, which are homologous to sequences on the F plasmid. Once integrated, the F plasmid is referred to as an episome.

Mechanism of Gene Transfer[edit]

During bacterial conjugation, an Hfr cell can transfer part of its chromosomal DNA to a recipient F- cell. The transfer begins at the origin of transfer (oriT) on the integrated F plasmid and proceeds in a linear fashion. However, because the entire chromosome is rarely transferred, the recipient cell usually remains F- but acquires new genetic material from the donor.

Significance in Genetic Mapping[edit]

Hfr cells are instrumental in genetic mapping of bacterial chromosomes. By analyzing the sequence and timing of gene transfer during conjugation, researchers can determine the relative positions of genes on the chromosome. This technique, known as interrupted mating, has been used extensively in Escherichia coli to map its genetic material.

Differences from F+ Cells[edit]

While both Hfr and F+ cells contain the F plasmid, the key difference lies in the integration of the plasmid into the chromosome in Hfr cells. F+ cells have the F plasmid as an independent, circular DNA molecule, whereas in Hfr cells, the plasmid is integrated into the host's chromosomal DNA.

Related Pages[edit]

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-'''Hfr cell''' is a bacterium that has been infected by a [[bacteriophage]] and has incorporated the bacteriophage's DNA into its own [[chromosome]]. This incorporation allows the bacterium to transfer its own chromosomal DNA to a recipient bacterium during [[conjugation]], a process known as high-frequency recombination (Hfr).
+== Hfr Cell ==
-== Overview ==
+An '''Hfr cell''' (High frequency of recombination) is a bacterium with a conjugative plasmid integrated into its chromosomal DNA. This integration allows the bacterium to transfer part of its chromosomal DNA to a recipient cell during [[bacterial conjugation]]. The process of Hfr formation and the subsequent genetic exchange play a crucial role in bacterial genetics and the study of [[gene mapping]].
-Hfr cells were first discovered by [[Luca Cavalli-Sforza]] in 1951. They are a type of [[F+ cell]], which are bacteria that contain the F (fertility) factor. However, unlike regular F+ cells, Hfr cells have the F factor integrated into their chromosome. This allows them to transfer chromosomal DNA to a recipient [[F- cell]] during conjugation.
+[[File:Hfr_Recombination.png|thumb|right|Diagram illustrating the process of Hfr recombination.]]
-== Conjugation ==
+=== Formation of Hfr Cells ===
-During conjugation, the Hfr cell forms a [[pilus]] that connects it to the recipient F- cell. The Hfr cell then begins to transfer its DNA to the F- cell. The transfer starts at the F factor and continues until the conjugation is interrupted. Because the F factor is usually the last part of the DNA to be transferred, the recipient cell rarely receives the entire F factor and therefore does not become an Hfr cell.
+Hfr cells are formed when an [[F plasmid]] (fertility plasmid) integrates into the bacterial chromosome through a process called [[homologous recombination]]. This integration occurs at specific sites on the chromosome, known as insertion sequences, which are homologous to sequences on the F plasmid. Once integrated, the F plasmid is referred to as an episome.
-== Significance ==
+=== Mechanism of Gene Transfer ===
-Hfr cells are important in [[genetic engineering]] and [[molecular biology]] because they allow for the transfer of large amounts of genetic material. This can be used to create [[genetic map]]s or to introduce new traits into a population of bacteria.
+During bacterial conjugation, an Hfr cell can transfer part of its chromosomal DNA to a recipient [[F- cell]]. The transfer begins at the origin of transfer (oriT) on the integrated F plasmid and proceeds in a linear fashion. However, because the entire chromosome is rarely transferred, the recipient cell usually remains F- but acquires new genetic material from the donor.
-== See also ==
+=== Significance in Genetic Mapping ===
-* [[Bacterial conjugation]]
+Hfr cells are instrumental in [[genetic mapping]] of bacterial chromosomes. By analyzing the sequence and timing of gene transfer during conjugation, researchers can determine the relative positions of genes on the chromosome. This technique, known as interrupted mating, has been used extensively in [[Escherichia coli]] to map its genetic material.
-* [[F factor]]
-* [[Genetic recombination]]
+=== Differences from F+ Cells ===
-== References ==
+While both Hfr and [[F+ cells]] contain the F plasmid, the key difference lies in the integration of the plasmid into the chromosome in Hfr cells. F+ cells have the F plasmid as an independent, circular DNA molecule, whereas in Hfr cells, the plasmid is integrated into the host's chromosomal DNA.
-<references />
+== Related Pages ==
-{{stub}}
+* [[Bacterial conjugation]]
+* [[F plasmid]]
+* [[Gene mapping]]
+* [[Escherichia coli]]
-[[Category:Bacteria]]
+[[Category:Microbiology]]
 [[Category:Genetics]]
-[[Category:Molecular biology]]