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SARS-CoV-2 is no Ferrari among viruses when it comes to mutations. Scientists reckon that its 30,000-base RNA genome acquires around two single-letter mutations a month, a rate around half as fast as influenza and one-quarter the rate of HIV. But allowed to multiply and jump from body to body for more than a year, SARS-CoV-2 has inevitably flourished into a genetically diverse tree branching into countless different variants.
Many variants—defined by a specific assortment of mutations—are relatively unremarkable. But scientists have been keeping a close watch on three rapidly spreading variants—first identified in the UK, South Africa, and Brazil—which harbor an unusual constellation of mutations. They all share a mutation called N501Y that affects the receptor binding domain (RBD) of the spike protein, which the virus uses to clasp onto human cells’ receptors and enter them. That mutation replaces SARS-CoV-2’s 501st amino acid, asparagine, with tyrosine, ...
