Biomedical Engineering Reference
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p
p
p
p
p
p
p
p
p
Rare
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
Desirable
and more usual
p
p
p
p
p
p
p
p
p
p
p
FIGURE 16.14
Segregational instability: a dividing cell donates all its active protein-making plasmids
p
to one
progeny and none to the other.
attached to each other to form a single unit. The process of multimerization involves using
host cell recombination systems. A dimer is a replicative unit in which two separate plasmids
have been joined, and a tetramer is a single unit consisting of four separate monomers fused
together.
Example 16-5
Segregational loss
What fraction of the cells undergoing division will generate a plasmid-free cell if:
(a)
All cells have 64 plasmids at division?
(b)
All cells have enough plasmid DNA for 64 copies, but one-half of the plasmid DNA is in
the form of dimers and one-eighth in the form of tetramers?
(c)
Half of the cells have 32 copies of the plasmid and half have 96 copies (the average copy
number is 64 as in case a)?
Solution
(a)
If we assume a random distribution at division, the probability of forming a plasmid-
free cell is given by Eqn
(16.38)
or
P ¼ 2
1P
R
For P
R
¼
64 and P
¼
1.084
10
19
plasmid-free cells per division.
(b)
If the total amount of plasmid DNA is equivalent to 50 single copies, we can determine
the plasmid distribution from
MþDþT ¼ 64
monomer plasmid equivalents
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