Viral genome excision

Most temperate phages encode an integrase for both integration and excision. Excision may require an accessory protein called excisionase or recombination directionality factor to promote excision Excision is the recombination event that leads to the release of a viral genome that was formerly integrated into the host DNA chromosome as a provirus. This release is usually induced upon changes in the host cell physiology (induction).

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NB. Aberrant excision may occur. Small pieces of bacterial DNA may become excised and packaged into the bacteriophage capsid together with the bacteriophage genome. This exchange of genetic information is called transduction .