24 Questions
What is the process of transferring genetic material from one organism to another that is not its direct descendant?
Horizontal Gene Transfer
How many mechanisms of Horizontal Gene Transfer are described in the text?
3
What is the role of RecA proteins in Transformation?
They promote genetic exchange between the donor's DNA and the recipient's DNA
Under what conditions does natural Transformation usually occur?
During a decrease in rate or a blockage of DNA synthesis
What is the term for the uptake of exogenous DNA by a competent cell?
Transformation
What is the term for the ability of bacterial cells to take up DNA from the medium or environment?
Competence
Which of the following bacteria is capable of artificial competence?
All of the above
What is the purpose of a sex pilus in conjugation?
To enable direct contact between the donor and recipient cells
Which method of transformation involves a temporary increase in the permeability of the bacterial membrane?
Electroporation
What is the role of the donor cell in conjugation?
To contain the conjugative/F plasmid
Which of the following is a characteristic of natural competence?
It is not coded by the bacterial genes
What is the result of the transfer of the F-plasmid during conjugation?
Both the donor and recipient cells contain a single strand of the F-plasmid
What is the result of the transfer of the F plasmid to an F- recipient cell?
The recipient cell becomes an F+ cell
What is the mechanism of replication adopted by certain plasmids?
Rolling circle replication
What type of cells are involved in the transfer of chromosomal genes?
Hfr and F- cells
What is the process by which bacteriophages transfer DNA from one cell to another?
Transduction
What type of transduction involves the packaging of DNA from any portion of the host genome inside the mature virion?
Generalized transduction
What is the role of the replication initiator protein in rolling circle replication?
To generate the primer for leading-strand initiation
What is the primary difference between generalized and specialized transduction?
Specialized transduction involves the integration of host DNA from a specific region into the viral genome.
What is the outcome of a bacteriophage infection in a lytic cycle?
The host cell is broken open and destroyed.
What is the role of a prophage in a lysogenic cycle?
It integrates into the host genome and becomes dormant.
What is the primary difference between a lytic and a lysogenic cycle?
A lytic cycle results in the death of the host cell, while a lysogenic cycle allows the host to survive.
What is the name of the bacteriophage that is known to follow both the lytic and lysogenic cycles?
Phage lambda
What is the term for the integrated viral genome in a host cell?
Prophage
Study Notes
Horizontal Gene Transfer (HGT)
- HGT is the process of transferring genetic material from one organism to another that is not its direct descendant.
- It permits the acquisition of evolutionary novelties.
- There are three mechanisms of HGT: Transformation, Transduction, and Conjugation.
Transformation
- Involves the uptake of exogenous DNA by a competent cell.
- DNA can come from native bacterial chromosome fragments, plasmid, or bacteriophage DNA.
- Transformation does not require cell-cell contact.
- RecA proteins promote genetic exchange between a fragment of the donor's DNA and the recipient's DNA.
- Natural competence can be induced by nutritional shift-down, which coincides with a decrease in rate or a blockage of DNA synthesis.
- Artificial competence can be achieved through chemical treatment and heat shock, or electroporation.
Conjugation
- Requires cell-to-cell contact (mating) between a donor cell and a recipient cell.
- A plasmid-encoded mechanism that involves the formation of a sex pilus, physical contact, and the transfer of the F-plasmid.
- The F-plasmid is replicated using a rolling circle mechanism.
- The recipient cell becomes a donor cell after receiving the F-plasmid.
Transduction
- Involves the transfer of DNA from one cell to another by bacteriophages.
- There are two types of transduction: generalized and specialized.
- Generalized transduction involves the packaging of DNA from any portion of the host genome into the mature virion.
- Specialized transduction involves the integration of DNA from a specific region of the host chromosome into the virus genome.
- Bacteriophages can have a lytic or lysogenic cycle, and some can carry out both.
Test your understanding of Horizontal Gene Transfer, a process that allows organisms to acquire genetic material from other organisms outside of their direct lineage. This quiz covers the three mechanisms of HGT, including transformation, transduction, and conjugation. Assess your knowledge of this crucial concept in evolutionary biology.
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