My understanding is that the interesting bit is not about the misalignment, but rather the fact that the furin site is an insertion, not a mutation. Additionall

My understanding is that the interesting bit is not about the misalignment, but rather the fact that the furin site is an insertion, not a mutation. Additionally, a non-canonical codon that encodes a restriction site. The idea as I understand is something like this: 1) I want to study what makes coronaviruses go from infecting bats to infecting humans 2) I add a furin site because my hypothesis is that a furin in the spike protein is important (because other coronaviruses like MERS have it) 3) I then try to passage the virus through many generations to see if it preserves the furin site I added (i.e. selects for it) because if it mutates at less than baseline, I know it's important (this also explains the "mosaic" aspect of the other mutations in the virus) 4) To be able to track that, when I add the furin site, I make sure to insert a restriction site that isn't found elsewhere in the genome, so I can do a quick RNA extraction, and restriction digest to see if it's preserved. Please note. That is my understanding of this one aspect of the lab leak hypothesis. It's not necessarily what I believe to be true. Additionally, it is not the only piece of evidence cited as part of the lab leak hypothesis, either.