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In that case, they spelled it: CGG ATC AGG CGC So they created 3 R's, and only one of them was CGG. The two adjacent R's were AGG CGC
Scientists have several programs that they use, to recommend codons. None of those programs would have recommended CGG CGG in this spot.
I think I first heard the CGG CGG claim when Yuri Deigin went on Bret Weinstein's show. It turns out Yuri isn't even the first guy to come up with this idea. When he first looked at SARS-CoV-2 he wrote a long blog post on why he thinks it's engineered. <a target="_blank" href="https://yurideigin.medium.com/lab-made-cov2-genealogy-through-the-lens-of-gain-of-function-research-f96dd7413748" color="blue">yurideigin.medium.com/lab-made-cov2-…</a>
In that blog post, he wrote a whole section on “codon usage”, where he carefully compared SARS2 with RATG13, SARS1, and several other viruses. Despite all that work, he never even noticed the double CGG.
It looks like he first learned about it from some random guy on Twitter, on May 2020.
So, this was never an obvious part of the lab leak theory, and it hasn't been embraced by all lab leak theorists.
It's more like: people have just tried creating lots of different versions of the lab leak theory and it evolves to include the most popular claims. The CGG CGG theory has grown to be one of the most popular claims.
Since there's no evidence that engineers actually prefer CGG codons, you could have used other letters to make this theory. Notice that CGA and CGC are also rare in bat viruses and more common in human DNA.
If the sequence had been CGA CGA or CGC CGC, Yuri could have just as easily said that those are the codons that engineers prefer -- the claim would be made up, either way.
Suppose that you live in some state where license plates usually have 3 letters and 3 numbers.
If you see a license plate where the numbers are 000, that's unlikely, the odds are 1 in 1,000 of finding that, just like the odds are 1 in 1,000 of CGG CGG.
If you also knew that scientists always have license plates that say 000, then that might be good evidence that car was driven by a scientist.
But if scientists don't actually have special license plates, then this is not actually meaningful. 000 is unlikely, but so is 111 or 222 or 333 or 459. Each of those numbers is 1 in 1,000.
You could see some random number and tell people, "that's the license plate scientists always have". But that's meaningless, because you could have pretended that's true for any number. That's basically what Yuri Deigin and Steven Quay did, with the CGG codons theory.
Okay, so the theory that scientists love using double CGG codons is made up. But I still haven't explained why SARS-CoV-2 has rare codons here, if Covid is natural.
Science doesn't have a perfect answer for that -- if the virus evolved naturally, no one consciously made that choice, so we can't say what nature was thinking at the time. But we do have some guesses for why it's there.
One experiment tried mutating away the CGG codons. <a target="_blank" href="https://pmc.ncbi.nlm.nih.gov/articles/PMC8235447/" color="blue">pmc.ncbi.nlm.nih.gov/articles/PMC82…</a> (from CGG CGG to AGG AGG) They found that the updated virus was less infectious than the one using CGG.
The issue had to do with protein folding. Their updated version made more spike protein, but the proteins folded less accurately. The CGG codons slow down the protein translation, and that improves folding accuracy. That may be the reason why evolution favors this.
If the CGG CGG was unnatural, or nature selected against it, then it would mutate into some other spelling of RR, over time. You can change only one letter of CGG in 4 different ways and still get R. It could change to CGA, CGT, CGC, or AGG.
We’ve now had millions of covid cases around the world. As of mid 2021, after 18 months of evolution, CGG CGG was still found in 99.85% of them. As of 2025, it was found in 99.6%.