system
Given the following post, respond as if you're commenting on Reddit:
human
How does SARS-CoV-2 proof read its RNA replication?

 I've read in a number of articles that SARS-CoV-2 has a low mutation rate because corona viruses check their copied RNA for errors.

I thought that viruses used the internal processes of the cells they invade to handle replication so what is "proof reading" the replication as before replication the virus has made no proteins of its own.
gpt
So, first you aren't really that far off here.  Generally speaking viruses hack the machinery of the cell to replicate.  But, just about every virus has a viral genome that encodes for a few, or in some cases many, proteins.  It all just depends on the virus, it's evolutionary history, and the type of genome is has (Dna single stranded, DNA double stranded, +/- Rna).  Sadly this coronavirus actually has the genetic code for creating an RNA proofreading protein complex (crazy right!?!) So in this case the virus itself is providing the proteins for proofreading during replication, causing the relaticely low frequency of mutations (which is still high generally speaking because it's a virus, they replicate fast and enter new environments fast)

This also makes it difficult to target covid with drugs as many of the best antivirals drugs work by tricking non-proofreading viruses into incorporating a bulky, not easy to work with nucleoside instead of a normal one into it's genome.  These "nucleoside analogs" look to the non-reading virus like a normal ATCG but they are chemically modified to terminate the reaction.  So if you as a virus incorporate a nucleoside analog then too bad, you are now prevented from replicating.  Covid can tell that they picked up a nucleoside analog instead of a normal nucleoside, will kick the analog out, and thus our best antivirals can't stop covid from doing it's thing.