Question: What residue is present at Spike position 681 in the strain of the virus that originally emerged in Wuhan?

Question: Name some lineages where this amino acid has mutated. What has it changed to?

Question: How many times has Spike position 212 mutated to S (serine) on this tree?

Question: What is the term for this multiple emergence of a mutation?

Question: Is there a pattern to the genetic background on which these mutations occur?

Question: What is a possible explanation for this pattern? Be as specific as possible

Question: What is this effect in which the genetic background determines what mutations are possible called?