Reassortment

changes in genomic composition that occur when host cells are co-infected with two segmented viruses that exchange whole genome segments.

can cause sudden alterations in the surface antigens of the viral progeny

e.g influenza

Transformation

the uptake of a naked DNA by a prokaryotic or eukaryotic cell.

In virology, this term may also be used to describe the incorporation of viral DNA into a host cell chromosome.

It alters the genetic composition of the host cell but typically causes no genomic change in progeny virions.

Recombination

gene exchange that occurs through the crossing over of two dsDNA molecules.

Genome recombination between two defective viruses co-infecting the same host cell can yield a cytopathic wild-type genome.

Phenotypic mixing

Co-infection of a host cell by two viral strains, resulting in progeny virions that contain nucleocapsid proteins from one strain and the genome of the other strain.

Since there is no change in the underlying viral genomes (no genetic exchange), the next generation of virions revert to their original unmixed phenotypes.

Interference