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SUMMARY:Patterns of purifying selection and adaptive evolution in SARS-CoV
 -2 - Professor Richard Neher\, Biozentrum\, University of Basel
DTSTART:20221117T140000Z
DTEND:20221117T150000Z
UID:TALK177065@talks.cam.ac.uk
CONTACT:Caroline Newnham
DESCRIPTION:Continued evolution and adaptation of SARS-CoV-2 has lead to m
 ore transmissible and immune-evasive variants with profound impact on the 
 course of the pandemic. Here I analyze the evolution of the virus over 2.5
  years since its emergence and estimate rates of evolution for synonymous 
 and non-synonymous changes separately for evolution within clades – well
  defined mono-phyletic groups with gradual evolution – and for the pande
 mic overall. The rate of synonymous mutations is found to be around 6 chan
 ges per year. Synonymous rates within variants vary little from variant to
  variant and are compatible with the overall rate. In contrast\, the rate 
 at which variants accumulate amino acid changes (non-synonymous mutation) 
 was initially around 12-16 changes per year\, but in 2021 and 2022 dropped
  to 6-9 changes per year. The overall rate of non-synonymous evolution\, t
 hat is across variants\, is estimated to be about 25 amino acid changes pe
 r year. This 2-fold higher rate indicates that the evolutionary process th
 at gave rise to the different variants is qualitatively different from tha
 t in typical transmission chains and likely dominated by adaptive evolutio
 n. I further quantify the spectrum of mutations and purifying selection in
  different SARS-CoV-2 proteins. Many accessory proteins evolve under limit
 ed evolutionary constraint with little short term purifying selection. Abo
 ut half of the mutations in other proteins are strongly deleterious and ra
 rely observed\, not even \nat low frequency.\n
LOCATION:Zoom meeting
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