Conjugation - SS1 Biology Lesson Note
Conjugation is a process of genetic transfer in which genetic material, such as plasmids or other DNA fragments, is transferred between two cells. It is most observed in bacteria but can also occur in other single-celled organisms.
Conjugation requires physical contact between the donor cell, which possesses the genetic material to be transferred, and the recipient cell, which receives the genetic material. The transfer is facilitated by a specialized appendage called the sex pilus or conjugation pilus.
The process of conjugation can be summarized as follows:
1. Donor cell formation: The donor cell contains a self-replicating circular DNA molecule known as a plasmid, which carries the genetic information to be transferred. The plasmid often contains genes that provide advantages to the recipient cell, such as antibiotic resistance.
2. Formation of the sex pilus: The donor cell synthesizes a sex pilus, a thin, elongated appendage composed of proteins. The sex pilus extends from the donor cell and establishes contact with the recipient cell.
3. Transfer of genetic material: Once the donor and recipient cells are in contact, a protein channel called the conjugation bridge is formed between them. The plasmid DNA is then transferred from the donor cell to the recipient cell through this channel.
4. Incorporation of genetic material: The recipient cell integrates the transferred genetic material into its own genome or, in the case of a plasmid, maintains it as an independent replicating unit. The recipient cell can then express the newly acquired genes and benefit from the traits encoded by the transferred DNA.
Conjugation provides a mechanism for horizontal gene transfer between bacteria, allowing for the spread of genetic material and the acquisition of new traits within a bacterial population. It plays a significant role in the evolution and adaptation of bacteria, particularly in the development of antibiotic resistance and the exchange of beneficial genes.
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Figure 63 image from wikipedia.org
It is important to note that conjugation is a specific form of genetic transfer and should not be confused with other processes such as reproduction or sexual reproduction, which involve the creation of offspring. Conjugation is a mechanism for genetic exchange between individual cells, contributing to genetic diversity and the survival of bacterial populations.