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CATEGORIES:Genetics Seminar 
SUMMARY:Patterns of purifying selection and adaptive evolu
 tion in SARS-CoV-2 - Professor Richard Neher\, Bio
 zentrum\, University of Basel
DTSTART;TZID=Europe/London:20221117T140000
DTEND;TZID=Europe/London:20221117T150000
UID:TALK177065AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/177065
DESCRIPTION:Continued evolution and adaptation of SARS-CoV-2 h
 as lead to more transmissible and immune-evasive v
 ariants with profound impact on the course of the 
 pandemic. Here I analyze the evolution of the viru
 s over 2.5 years since its emergence and estimate 
 rates of evolution for synonymous and non-synonymo
 us changes separately for evolution within clades 
 – well defined mono-phyletic groups with gradual e
 volution – and for the pandemic overall. The rate 
 of synonymous mutations is found to be around 6 ch
 anges per year. Synonymous rates within variants v
 ary little from variant to variant and are compati
 ble with the overall rate. In contrast\, the rate 
 at which variants accumulate amino acid changes (n
 on-synonymous mutation) was initially around 12-16
  changes per year\, but in 2021 and 2022 dropped t
 o 6-9 changes per year. The overall rate of non-sy
 nonymous evolution\, that is across variants\, is 
 estimated to be about 25 amino acid changes per ye
 ar. This 2-fold higher rate indicates that the evo
 lutionary process that gave rise to the different 
 variants is qualitatively different from that in t
 ypical transmission chains and likely dominated by
  adaptive evolution. I further quantify the spectr
 um of mutations and purifying selection in differe
 nt SARS-CoV-2 proteins. Many accessory proteins ev
 olve under limited evolutionary constraint with li
 ttle short term purifying selection. About half of
  the mutations in other proteins are strongly dele
 terious and rarely observed\, not even \nat low fr
 equency.\n
LOCATION:Zoom meeting
CONTACT:Caroline Newnham
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