this is recombination, portions of virus are swapped around, in this case an omicron spike, with wuhan backbone. this sort of manipulation can produce gain of

this is recombination, portions of virus are swapped around, in this case an omicron spike, with wuhan backbone. this sort of manipulation can produce gain of function when there is interplay between the recombined elements, most often it is simply a recombination of functions. to split hairs, the wuhan "backbone" [not spike] gained function of omicron spike, but lost function of wuhan spike. gain of function doesnt have to be so dramatic. there is a non spike region, of coronavirus that modulates virus/interferon signaling dynamics, modification of a small number of, [as in 2-3] codons will produce lethality that itself is not gain of function it is potentiation. a clear cut case of gain of function would be a recombination of wuhan backbone with chimeric SARS-MERS spike that retains both target specificities [ACE2-DPP4]