M13
Filamentous.
About 870nm in
length and 6nm in width.
Consists of single
stranded DND (ssDNA).
Three kinds of
capsomeres build the capside.
Infects E. coli by
adsorbing to the cell and entering through F pilli. Therefore only infect F+
and HFr cells. Also male specific.
Does not kill the
host. Particles are released by budding, therefore when the particles are
released, the host cell is alive.
An efficient vector
in gene cloning as it can hold longer pieces of foreign DNA.
T phage
Structure is
composed of icosahedral head, double stranded DNA and a tail.
Infects E.coli
Main types of T phages are T2, T4 and T12.
In the infection
linear DNA of the phage is released to the host cell and becomes circular by
replicating that later produces a long DNA chain known as ‘Concatamen’. This coils
into the phage’s head by headfull mechanism while packaging.
Infection kills the
host cell as the new particles are released outside by bursting the host cell.
Lambda (λ)
Composed of head
and tail.
Head is consisting of
double stranded linear DNA.
At both 5’ ends of
the DNA strand, 12 complementary base pair, single stranded segments are
present. These two ends are known as “cos ends”.
Because of the cos
ends, phage chromosome circularizes before replication. Concatamen is produced
during the replication and during the packaging, Terminase enzyme cuts off the
cos ends.
Host cell is E.coli.
MS2
Contains the
smallest known genome.
Super coiled single
stranded DNA.
Infect only through
sex pilli. Therefore male specific.
Infect E.coli.
Phi×174(ΦX174)
Contains a single
stranded circular DNA.
After adsorption,
synthesizes the complementary strand and becomes double stranded.
Use as a positive
control in DNA sequencing.
G4
Structurally
similar to ΦX174 phage.
Can infect susceptible
E.coli cells.
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