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## Viral Genetics ### Recombination - Exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology. ### Reassortment - When viruses with segmented genomes (eg, influenza virus) exchange genetic material. - **Example:** The 2009 novel H1N1 influenza...

## Viral Genetics ### Recombination - Exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology. ### Reassortment - When viruses with segmented genomes (eg, influenza virus) exchange genetic material. - **Example:** The 2009 novel H1N1 influenza A pandemic emerged via complex viral reassortment of genes from human, swine, and avian viruses. - Has potential to cause antigenic shift. Reassortment of genome segments. ### Complementation - When 1 of 2 viruses that infect the cell has a mutation that results in a nonfunctional protein - The nonmutated virus “complements” the mutated one by making a functional protein that serves both viruses. - **Example:** Hepatitis D virus requires the presence of replicating hepatitis B virus to supply HBsAg, the envelope protein for HDV ### Phenotypic Mixing - Occurs with simultaneous infection of a cell with 2 viruses. - For progeny 1, genome of virus A can be partially or completely coated (forming *pseudovirion*) with the surface proteins of virus B. - Type B protein coat determines the tropism (infectivity) of the hybrid virus. - Progeny from subsequent infection of a cell by progeny 1 will have a type A coat that is encoded by its type A genetic material.