Bacteriophages
1) Viruses specifically infect bacteria.
2) Phages have simple structure: Genetic material
(DNA or RNA) is encapsulated in a protective
proteineous coat called caspid.
3) It replicates within the bacteria and lysis them.
Bacteriophage
λ in Gene cloning
* It’s an
E.Coli virus that can carry an insert of a range between 15-20 kb
* After Bacteriophage λ infects the E.Coli, two
things may happen:
a) Lytic cycle: where the phage replicates within
cell and finally lysis the cell inorder to release 100 of phage particles and
this occurs in 20 minutes.
b) Lysogenic cycle: the phage DNA can be
incorporated into the bacterial genome as a prophage and maintained as a benign
guest through successive cell divisions.
But under environmental circumstances, the integrated
phage DNA is excised out and therefore the phage enters the lytic cycle.
* The length of the Bacteriophage λ is 50kb and
integration-excision (I/E) events occurs at 20 kb respectively.
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