What are the facts that determine plasmid copy number?
Plasmids are extrachromosomal DNA elements with characteristics copy number within the host. Although plasmid copy number may vary in different bacteria,within a given host,and under fixed growth conditions,any particular plasmid has a characteristics copy number.This is achieved by :-
Plasmid-encoded control elements that regulate the initiation of the replication step.To define and to maintain the copy number,plasmids use definitive regulatory circuits.Negative regulators(inhibitors),acting at the initiation step,were involved in this control.The control system does adjustments in the plasmid copy number by either increasing or decreasing the rate of replication per plasmid copy per cell cycle.The molecules involved directly in the control can be :
(ii)DNA sequences (iterons or negative regulators)
(iii)antisense RNA and proteins(repressor) acting in concert