Bacteriophages Flashcards
1
Q
What is a bacteriophage?
A
Virus that infects bacteria; made up of a protein called capsid that encloses DNA/RNA as genome; genes in the genome are those that code for the capsid and replication gene for DNA/RNA
2
Q
Bacteriophage lambda
A
Attaches itself to outside of bacterial cell and injects its DNA into the host cell
DNA is linear and double-stranded
DNA contains single-stranded complementary ends of 12 nucleotides (cohesive ends)
3
Q
Bacteriophage lambda- process of infection
A
- DNA is circularised by pairing of cohesive ends
- It is then integrated into the host cell genome then transferred to daughter cells through cell division
- Foreign DNA is excised from host genome
- New phage particles are produced
4
Q
Cohesive ends
A
- Known as cos sites
- Important as they enable the DNA to be circularised, which is needed for insertion into host genome
- As, act as recognition sites for endonuclease that cut at cos sites and produce individual genome
5
Q
Bacteriophage lambda- process of infection (lytic cycle)
A
- Phage DNA control cell’s metabolism to produce viral particles
- Phage heads produced and packed with phage DNA
- Collars, sheaths and tail fibers are attached to heads
- Cell lyses and releases mature phages
6
Q
Bacteriophage lambda- process of infection (lysogenic cycle)
A
- Phage DNA incorporated into host genome
- DNA replicated along with bacterial DNA prior to binary fission
- Binary fission, each cell has phage DNA
- Enters lytic cycle
7
Q
Bacteriophage M13
A
- Small, single-stranded, 10 kb
- Injection of DNA into host cell through pilus
8
Q
Bacteriophage M13- process of infection
A
- DNA synthesises complementary strand to form a double-stranded component called Replicative form (RF)
- Original strand is (+) while complementary is (-) and (+) is packed in the new phage heads
- RF can be used as a plasmid in recombinant DNA technology
