Chapter 8: Microbial Genetics - Horizontal Gene Transfer Flashcards
1
Q
What are plasmids?
A
- self-replicating dsDNA molecules
2
Q
What do plasmids contain?
A
- non-essential genes (not needed for survival)
ex. genes for toxin production
3
Q
What are F plasmids? (2)
A
- fertility factors
- carry genes to make F pilus (sex pilus)
4
Q
Where are F plasmids involved in?
A
conjugation
5
Q
What are R plasmids? (2)
A
- resistance factors
- carry genes for antibiotic resistance
6
Q
What are vir plasmids? (2)
A
- virulence factors
- carry genes for toxin production
7
Q
What are three methods of horizontal gene transfer in bacteria?
A
- Transformation
- Transduction
- Conjugation
8
Q
What occurs in transformation? (4)
A
- pieces of “naked” DNA are taken up by a bacterial cell
- these pieces can then be integrated into the chromosome
- recombination
- can then be passed to progeny and become a stable part of the genome
9
Q
Where can transformation occur?
A
- from dead cells, or released from plasmids
10
Q
In lecture, what occurs in transformation?
A
free DNA is incorporated into chromosomal DNA
11
Q
What is transduction?
A
- small fragments of DNA transferred between bacteria by bacteriophage
12
Q
What are bacteriophages?
A
viruses that infect bacteria
13
Q
What are the steps in transduction? (5)
A
- Phage attaches to bacterial cell wall
- Injects its DNA into the cell
- Phage DNA is replicated inside bacterial cell wall
- Phage DNA also encodes enzymes that cut the bacterium’s DNA into fragments
- As new phages are being assembled, some accidentally receive a piece of bacteria DNA instead of phage DNA, creating a transducing particle
14
Q
In lecture, what are the most important microbes in the biosphere?
A
- DNA phages
15
Q
Are viruses living?
A
no
18
Q
How does conjugation occur? (4)
A
- Donor cell (F+) forms an f pilus and uses it to attach to a recipient cell F-)
- pilus retracts to bring cells together
- the donor cell replicates the F factor as a copy is passed to the recipient
- The recipient becomes an F+ cell
