Cell Biology
Bacterial recombination is the transfer of DNA from one bacterium to another to create genetic diversity. It occurs in three main ways: transformation, conjugation, and transduction. Transformation occurs when foreign DNA from the environment is integrated into the genome of the bacterial host cell, typically originating from other lysed bacteria. Conjugation is the transfer of genetic material from one bacterium to another and is considered the prokaryotic form of sexual reproduction. In conjugation, the bacterium sharing genetic material is called the donor male, and the bacterium receiving it is the recipient female. The sharing of genetic material occurs via direct contact between the cells, facilitated by an appendage called a sex pilus. However, only cells with a special chunk of DNA called the fertility factor (F-factor) can synthesize the proteins needed to make up the sex pilus.
Lastly, transduction occurs when a virus that infects bacteria, called a bacteriophage, transfers genetic material from one bacterium to another. Bacteriophages can accidentally incorporate a piece of bacterial DNA into their own viral genome when reproducing inside the host. When one of these phages infects another bacterium, it releases the mix of viral and bacterial genes into the new host cell, resulting in new genes for the host.
Lesson Outline
<ul> <li>Introduction to Bacterial Recombination <ul> <li>Need for genetic variation in bacteria</li> <li>Three main ways of bacterial recombination: transformation, conjugation, and transduction</li> </ul> </li> <li>Transformation <ul> <li>Foreign DNA from the environment integrated into the bacterial genome</li> <li>Typical source of genetic material: lysed bacteria</li> </ul> </li> <li>Conjugation <ul> <li>Transfer of genetic material from one bacterium to another</li> <li>Donor male and recipient female bacteria</li> <li>Direct cell contact and the use of a sex pilus for DNA transfer</li> <li>Fertility factor (F-factor) required for sex pilus formation and DNA transfer</li> <li>Recipient female can become a donor male if F-factor is transferred</li> </ul> </li> <li>Transduction <ul> <li>Transfer of genetic material by bacteriophages (viruses)</li> <li>Bacteriophages reproduce inside host and can accidentally incorporate bacterial DNA</li> <li>Transfer of mixed viral and bacterial genetic material to a new bacterial host</li> </ul> </li> </ul>
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FAQs
Genetic recombination is a process by which genetic material from two different sources is combined to create a new genetic makeup, leading to genetic variation. In bacteria, this can occur through transformation, conjugation, and transduction. On the other hand, binary fission is a type of asexual reproduction in bacteria, where the parent cell divides into two equal daughter cells, each with an identical copy of the parent cell's DNA. Binary fission does not typically involve genetic variation, while genetic recombination promotes genetic diversity in bacterial populations.
Transformation, conjugation, and transduction are three mechanisms by which bacteria exchange genetic material, leading to genetic recombination. In transformation, bacteria take up free DNA molecules present in the environment, which can then be integrated into their own genome. Conjugation involves direct cell-to-cell contact, where DNA transfer takes place through a sex pilus. Transduction is a process in which a bacteriophage (a virus that infects bacteria) transfers DNA from one bacterium to another unintentionally. All three mechanisms lead to the incorporation of new genetic material into the recipient bacteria, increasing the genetic variation within the bacterial population.
The sex pilus is a tube-like structure present on the surface of the donor bacterial cell in conjugation. It connects the donor and recipient cells, allowing for the transfer of genetic material between them. The fertility factor (F factor) is a specific plasmid (small, circular DNA molecule) that allows the bacterial cell to form a sex pilus and transfer genetic material. The donor cell contains the F factor, while the recipient cell typically does not (though the F factor plasmid can be transferred from the donor cell to the recipient during conjugation).
Transduction occurs when a bacteriophage infects a bacterial cell and accidentally packages a fragment of the host bacterium's DNA into its viral capsid instead of its own genetic material. When the newly assembled bacteriophage infects another bacterium, it injects the previously packaged bacterial DNA into the new host. This foreign DNA can be integrated into the new host bacterium's genome, resulting in genetic recombination and an increase in genetic variation within the bacterial population.
