Transformation, Transduction and Conjugation (Horizontal Gene Transfer in Bacteria)

Summary

This script discusses horizontal gene transfer, contrasting it with vertical gene transfer. It outlines three subtypes: transformation, transduction, and conjugation. Transformation is the uptake of free DNA by bacteria, which can be induced artificially. Transduction involves viruses transferring genetic material between cells. Conjugation is a direct cell-to-cell transfer of DNA, facilitated by a sex pilus. The video provides insight into these processes and their implications in genetics.

Takeaways

• 🧬 Gene transfer can be either vertical (from parent to offspring) or horizontal (between organisms).
• 🔄 Horizontal gene transfer includes transduction, conjugation, and transformation.
• 🌐 Transformation is the uptake of free DNA by a bacterium, which can provide a selective advantage.
• 🧪 Natural competence for DNA uptake is limited to certain bacteria, but can be induced in the lab.
• 🔥 Heat shock transformation uses calcium chloride and heat to make bacterial cells permeable to DNA.
• 🦠 Transduction involves the transfer of genetic material via viruses, like bacteriophages, which can accidentally package bacterial DNA.
• 🧬 In transduction, viral vectors can integrate foreign DNA into a host cell's genome.
• 🤝 Conjugation is a unidirectional transfer of DNA between bacteria that requires cell-to-cell contact.
• 🔬 The donor bacterium in conjugation contains an 'fertility factor' or F plasmid, making it 'F+'.
• 🌉 The sex pilus is a structure that connects donor and recipient bacteria, facilitating DNA transfer.
• 🔄 After conjugation, the recipient bacterium also contains the F factor and becomes 'F+'.

Q & A

What is the generic term for subtypes of gene transmission among organisms?

The generic term is horizontal gene transfer.

How is vertical gene transfer different from horizontal gene transfer?

Vertical gene transfer involves the transmission of genetic material from parent to offspring through sexual or asexual reproduction, while horizontal gene transfer occurs between two already existing organisms that are not offspring of each other.

What are the different subtypes of horizontal gene transfer mentioned in the script?

The different subtypes of horizontal gene transfer mentioned are transduction, conjugation, and transformation.

What is transformation in the context of gene transfer?

Transformation is the uptake of free genetic material from the environment by a bacterium, which can include plasmid DNA released by other bacteria.

What is competence in bacteria?

Competence in bacteria refers to the ability to take up free DNA from the environment.

How can competence be induced in bacteria in a laboratory setting?

Competence can be induced in bacteria by chemical modifications, such as using a heat shock transformation protocol involving calcium chloride and a short heat shock.

What is transduction in the context of gene transfer?

Transduction is the transmission of genetic material between cells carried out by viruses, such as when a bacteriophage infects a bacterial cell and accidentally packages bacterial DNA along with its own when forming new virus particles.

How does conjugation facilitate horizontal gene transfer between bacterial cells?

Conjugation involves cell-to-cell contact where one bacterial cell (the donor) transfers genetic material to another (the recipient), often through an extending structure called the sex pilus.

What is the role of the F plasmid in bacterial conjugation?

The F plasmid is found in the donor bacteria and is responsible for the formation of the sex pilus, which facilitates the transfer of genetic material to the recipient bacteria.

How does the recipient cell change after receiving DNA through conjugation?

After receiving DNA through conjugation, the recipient cell also contains the F factor and can be considered F positive, allowing it to potentially transfer genetic material to other cells in the future.

What is the significance of horizontal gene transfer in the evolution of organisms?

Horizontal gene transfer can introduce new genetic traits into a population quickly, potentially providing selective advantages and contributing to the diversity and evolution of organisms.