F plasmid: Difference between revisions
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The F plasmid is an example of a large [[Plasmid|plasmid]] which contains genes that allow the plasmids [[DNA|DNA]] to be transferred between cells. It is found in the bacterium [[E. coli|''E. coli'']]; [[E. coli|''E. coli'']] containing this F factor are known as F<sup>+ </sup>and those without are known as F<sup>-</sup>. The F stands for fertility and the F factor is around 100000 bases in length. The F<sup>+</sup> cells have a tube like structure called a [[Pilus|pilus]] which allows it to make contact with F<sup>-</sup> cells. This joining via a pilus in order to transfer DNA between bacteria | The F plasmid is an example of a large [[Plasmid|plasmid]], which contains genes that allow the plasmids [[DNA|DNA]] to be transferred between cells. It is found in the bacterium [[E. coli|''E. coli'']]; [[E. coli|''E. coli'']] containing this F factor are known as F<sup>+ </sup>and those without are known as F<sup>-</sup>. The F stands for fertility and the F factor is around 100000 bases in length. The F<sup>+</sup> cells have a tube-like structure called a [[Pilus|pilus]], which allows it to make contact with F<sup>-</sup> cells. This joining via a pilus in order to transfer DNA between bacteria is known as [[Reproduction by Conjugation|conjugation]]. Therefore the F plasmid is known as a [[Conjugative plasmid|conjugative plasmid]]. Within the [[E. coli|''E. coli'']] cells, the F plasmid has one or two copies making it a low-copy-number plasmid. During the cell cycle, it replicates once and segregates to both daughter cells<ref>Information and ideas gained from chapter 9, pgs304-305, HartlL. and RuvoloM., (2011) Genetics: Analysis of Genes and Genomes, 8th Edition, Burlington, Jones and Bartlett Learning.</ref>. | ||
=== Transmission of the F plasmid. | === Transmission of the F plasmid. === | ||
Within the F factor are genes which governs the maintenance and transmission of the F plasmid. As already mentioned, the F plasmid is transferred via [[Reproduction by Conjugation|conjugation]] which occurs due the [[Pilus|pilus]] known as the F pilus. All the proteins that are associated with the F pilus are [[Transcription|transcribed]] and [[Translation|translated]] from genes within the F factor. The F plasmid is not transferred to a F<sup>-</sup> cell via the F pilus, the F pilus merely pulls the two cells together allowing a [[Conjugative junction|conjugative junction]] to form which contains a pore that allows the DNA to pass from the F<sup>+</sup> cell to the F<sup>-</sup> cell. During transfer, the F plasmid unwinds and the outer strand breaks which will be the one that is transferred to the F<sup>-</sup> cell via the pore in the [[Conjugative junction|conjugative junction]]. Replication of the plasmid then takes place in order to make both single strands of DNA into double stranded DNA plasmids. In the original F<sup>+</sup> cell, the | Within the F factor are genes, which governs the maintenance and transmission of the F plasmid. As already mentioned, the F plasmid is transferred via [[Reproduction by Conjugation|conjugation]], which occurs due to the [[Pilus|pilus]] known as the F pilus. All the proteins that are associated with the F pilus are [[Transcription|transcribed]] and [[Translation|translated]] from genes within the F factor. The F plasmid is not transferred to a F<sup>-</sup> cell via the F pilus, the F pilus merely pulls the two cells together allowing a [[Conjugative junction|conjugative junction]] to form, which contains a pore that allows the DNA to pass from the F<sup>+</sup> cell to the F<sup>-</sup> cell. During the transfer, the F plasmid unwinds and the outer strand breaks, which will be the one that is transferred to the F<sup>-</sup> cell via the pore in the [[Conjugative junction|conjugative junction]]. Replication of the plasmid then takes place in order to make both single strands of DNA into double-stranded DNA plasmids. In the original F<sup>+</sup> cell, the single strand merely undergoes [[Rolling circle replication|rolling circle replication]] to once again become double-stranded. In the recipient cell, the linear single-stranded DNA is replicated into a double strand and becomes a circular F plasmid containing the F factor<ref>Information and Ideas gained from chapter 9, pgs304-305, Hartl L. and Ruvolo M. (2011) Genetics: Analysis of Genes and Genomes, 8th edition, Burlington, Jones and Bartlett Learning.</ref>. | ||
Both ''[[E. coli|E. coli]]'' cells are now considered to be F<sup>+</sup> cells and therefore can both now transfer the F plasmid and therefore the F factor. This transfer only requires a few minutes although is not | Both ''[[E. coli|E. coli]]'' cells are now considered to be F<sup>+</sup> cells and therefore can both now transfer the F plasmid and therefore the F factor. This transfer only requires a few minutes although is not efficient in natural conditions meaning only 10% of naturally occurring ''E. coli'' cells contain the F plasmid and hence the F factor<ref>Information and ideas gained from Chapter 9, pgs 304-305, Hartl L. and Ruvolo M.(2011)Genetics: Analysis of Genes and Genomes, 8th edition, Burlington, Jones and Bartlett Learning.</ref>. | ||
NB: F plasmids are | NB: F plasmids are unusually large and can accept large scale inserts (up to 300 kB). | ||
=== References: === | === References: === | ||
<references /> | <references /> | ||
Latest revision as of 20:56, 5 December 2017
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. coli; E. coli containing this F factor are known as F+ and those without are known as F-. The F stands for fertility and the F factor is around 100000 bases in length. The F+ cells have a tube-like structure called a pilus, which allows it to make contact with F- cells. 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. Within the E. coli cells, the F plasmid has one or two copies making it a low-copy-number plasmid. During the cell cycle, it replicates once and segregates to both daughter cells[1].
Transmission of the F plasmid.
Within the F factor are genes, which governs the maintenance and transmission of the F plasmid. As already mentioned, the F plasmid is transferred via conjugation, which occurs due to the pilus known as the F pilus. All the proteins that are associated with the F pilus are transcribed and translated from genes within the F factor. The F plasmid is not transferred to a F- cell via the F pilus, the F pilus merely pulls the two cells together allowing a conjugative junction to form, which contains a pore that allows the DNA to pass from the F+ cell to the F- cell. During the transfer, the F plasmid unwinds and the outer strand breaks, which will be the one that is transferred to the F- cell via the pore in the conjugative junction. Replication of the plasmid then takes place in order to make both single strands of DNA into double-stranded DNA plasmids. In the original F+ cell, the single strand merely undergoes rolling circle replication to once again become double-stranded. In the recipient cell, the linear single-stranded DNA is replicated into a double strand and becomes a circular F plasmid containing the F factor[2].
Both E. coli cells are now considered to be F+ cells and therefore can both now transfer the F plasmid and therefore the F factor. This transfer only requires a few minutes although is not efficient in natural conditions meaning only 10% of naturally occurring E. coli cells contain the F plasmid and hence the F factor[3].
NB: F plasmids are unusually large and can accept large scale inserts (up to 300 kB).
References:
- ↑ Information and ideas gained from chapter 9, pgs304-305, HartlL. and RuvoloM., (2011) Genetics: Analysis of Genes and Genomes, 8th Edition, Burlington, Jones and Bartlett Learning.
- ↑ Information and Ideas gained from chapter 9, pgs304-305, Hartl L. and Ruvolo M. (2011) Genetics: Analysis of Genes and Genomes, 8th edition, Burlington, Jones and Bartlett Learning.
- ↑ Information and ideas gained from Chapter 9, pgs 304-305, Hartl L. and Ruvolo M.(2011)Genetics: Analysis of Genes and Genomes, 8th edition, Burlington, Jones and Bartlett Learning.