> Only about 5% of arginines in SARS-CoV-2 or RaTG13 are coded by CGG.(3) This implies that the CGGCGG in the inset would have an estimated 0.25% probability to

> Only about 5% of arginines in SARS-CoV-2 or RaTG13 are coded by CGG.(3) This implies that the CGGCGG in the inset would have an estimated 0.25% probability to “naturally” occur as an encoder of the RR motif Duplications are a common source of natural mutations, so I don't think it's right to multiply 5% like that (ie it's not an independent event) ie once a "CGG" exists, a single copying error makes "CGGCGG" rather than 2 independent events next to each other. We know genomes have repetitive sequences, but if you want to test, you could count 2x arginines in the viral sequence and seeing what the frequency is for the codons being different vs the same.