Genetic shift vs drift: Which describes major antigenic change via reassortment of RNA segments in segmented viruses such as influenza A?

Genetic shift vs drift: Which describes major antigenic change via reassortment of RNA segments in segmented viruses such as influenza A?

• A. Genetic drift
• B. Recombination
• C. Genetic Shift
• D. Antigenic Variation

Answer: (C)

Major antigenic change via reassortment of RNA segments in segmented viruses like influenza A is called genetic shift. When two different influenza strains infect the same cell, their segmented genomes can mix and swap whole segments, producing progeny with a novel combination of surface antigens such as hemagglutinin and neuraminidase. This abrupt shift can bypass existing herd immunity and spark pandemics. By contrast, genetic drift involves small, gradual changes from point mutations in those surface proteins, not a wholesale exchange of entire genome segments. Recombination is a different mechanism and isn’t the primary driver of these sudden antigenic revolutions in influenza. Antigenic variation is the broad idea of changing antigens, but the specific process described here—major, rapid change from segment swapping—matches genetic shift.

Major antigenic change via reassortment of RNA segments in segmented viruses like influenza A is called genetic shift. When two different influenza strains infect the same cell, their segmented genomes can mix and swap whole segments, producing progeny with a novel combination of surface antigens such as hemagglutinin and neuraminidase. This abrupt shift can bypass existing herd immunity and spark pandemics. By contrast, genetic drift involves small, gradual changes from point mutations in those surface proteins, not a wholesale exchange of entire genome segments. Recombination is a different mechanism and isn’t the primary driver of these sudden antigenic revolutions in influenza. Antigenic variation is the broad idea of changing antigens, but the specific process described here—major, rapid change from segment swapping—matches genetic shift.