Lecture 23: Horizontal Gene Transfers Flashcards
What is gene transfer?
The process by which genetic material is transferred from one organism to another.
What is vertical gene transfer?
The transmission of genetic material from parent to offspring.
What is horizontal gene transfer?
The transfer of genetic material between organisms that are not in a parent-offspring relationship.
What are the three types of horizontal gene transfer?
- Conjugation
- Transformation
- Transduction
Define recombination in the context of gene transfer.
Genes from a donor cell are passed to a recipient cell, and the DNA is combined into the recipient’s DNA.
What is a recipient cell called after recombination occurs?
Recombinant.
What are the three ways prokaryotes can pick up exogenous DNA?
- Conjugation * Transformation * Transduction
What is transformation?
The process by which DNA fragments are taken up by a recipient cell.
What happens to ssDNA during transformation?
It recombines with the host chromosome through homologous recombination.
What was the Griffith Experiment?
An experiment that demonstrated the transformation principle using two strains of Streptococcus pneumoniae.
What were the two strains of Streptococcus pneumoniae in the Griffith Experiment?
- S strain: smooth, pathogenic, with a capsule
- R strain: rough, nonpathogenic, without a capsule
What did Avery-MacLeod-McCarty demonstrate in 1944?
That DNA is the substance responsible for transformation.
What is the role of protease in the Avery-MacLeod-McCarty experiment?
It digests proteins to test if transformation still occurs.
What is the role of RNase in the Avery-MacLeod-McCarty experiment?
It digests RNA to test if transformation still occurs.
What is the role of DNase in the Avery-MacLeod-McCarty experiment?
It digests DNA, preventing transformation and allowing observation of outcomes.
What is a plasmid?
A small, double-stranded, circular piece of DNA that can replicate independently.
What are conjugative plasmids?
Plasmids that carry genes for conjugation, including pili production.
What are fertility (F) plasmids?
Conjugative plasmids that enable the transfer of genetic material between bacteria.
What are resistance (R) plasmids?
Plasmids that carry genes conferring resistance to antibiotics.
What are col plasmids?
Plasmids that contain genes to produce bacteriocins that kill other bacteria.
What are virulence plasmids?
Plasmids that contain genes making bacteria more virulent or pathogenic.
What are metabolic plasmids?
Plasmids that contain genes allowing bacteria to metabolize new substances.
What are the two types of conjugation?
- Plasmid Transfer
- Chromosome Transfer
Describe the steps in plasmid transfer during conjugation.
- Sex pilus binds to recipient cell
- Mobilization of DNA transfer
- Transfer of one strand of DNA
- Complementary strands synthesized in both cells
What is Hfr conjugation?
A process where an F plasmid integrates into the host chromosome, increasing gene transfer frequency.
What is transduction?
The process by which bacteriophages transfer genetic material from one bacterium to another.
What are the two cycles of the bacteriophage life cycle?
- Lytic Cycle
- Lysogenic Cycle
What is generalized transduction?
A process where any gene can be transferred during the lytic cycle.
What is specialized transduction?
A process where genes near the phage integration site are transferred during improper excision of the prophage.
What is the significance of transduction?
It contributes to genetic diversity among bacteria and provides insights into viral involvement in cancer.
