So... Can someone with bio/genetic/epidemiology background explain this to me? Are her claims valid? The criticism to this paper seems to be that the genetic variation is only 5% but isn't that large in genetic terms?

@kota her claims are not valid. She says "The genomic sequence of SARS-CoV-2 is "suspiciously" similar to that of a bat coronavirus discovered by military laboratories." This makes sense since it evolved from a coronavirus.

She said "The receptor-binding motif within the Spike (S) S protein of SARS-CoV-2 resembles a SARS-CoV virus from the 2003 epidemic, in what the authors describe as a "suspicious manner"." This makes sense since it connects to the ACE receptor in the lungs. It would have a specific shape in order to bind with it, otherwise it wouldn't bind.

"SARS-CoV-2 contains a furin-cleavage site at its S protein which enhances viral infectivity. This cleavage site is absent in this class of coronaviruses that are found in nature. The authors state that this suggests "strong possibility that this furin-cleavage site is not the product of natural evolution and could have been inserted into the SARS-CoV-2 genome artificially by techniques other than serial passage or recombination events."" While this is technically possible, it could also arise from natural selection. Random mutations happen all the time, and a Wet Market like where they suspect COVID came from is 100% the best place to have naturally formed viruses evolve since there are so many animals in close proximity.

@Demosthenes I also read the criticism of the pre-print. My original question was leaning more towards the critical claim that covid-19 does not vary enough from other Corona viruses found in nature to lead one to belief that it was artificially modified from an existing virus. So, what percentage of variation among coronaviruses would be high enough to arouse suspicion of genetic manipulation? In my poor (emphasis on poor) understanding of biology, a 5% variation could be significant. Is that not the case?

@kota in viruses, 5% isn't big. Most viruses are RNA-based which are very prone to damage and mutation since you've only got one copy of data to work with. When combined with the fact that it likely mutated between a couple species, 5% isn't much.

@kota to expand a bit, unlike mammalian DNA which has billions of base pairs and are kind of brittle, viral RNA are only composed of a few thousand base pairs. Sections of that RNA doesn't actually do anything, meaning mutations in those areas don't actually cause issues so aren't selected against. A couple hundred base pairs out of only a few thousand can be modified without issue, which is a big chunk of the total.

@Demosthenes 👨‍🔬I guess viruses are not as sophisticated as us. Thanks a lot for the clarification.

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