Natural Selection on SNP mutation in a Haploid Bacteriophage
Selection in a haploid system involves a selective
advantage for one or the other of two SNP alleles,
rather than a diploid genotype. Here, the SNP
in the MS2 RNA phage gene is C206U.
The notation indicates that the standard C base at
position 206 has mutated to a U base. The U
allele has a selective advantage: the graph shows the
increase in frequency of the U allele at intervals
of 25 generations. The error bars show variation
in the rate of fixation among replicate cultures. The
increase in f(U) is exponential, and the pre-existing
C allele is eliminated in some populations by 75 and
in all by 100 generations.
Contrast this to the behavior of a disadvantageous allele in
a diploid system, where it is never entirely
eliminated because when rare it show up only in
heterozygotes.
The haploid selection model accounts for the increase of the 'Delta' & 'Omicron' variants of the Covid-19 RNA virus. Whereas the example above describes a selective advantage in vitro, first the Delta and now the Omicron variants are at a selective advantage in vivo because of its higher infectivity rate (Ro, read as "R nought") relative to the original strain.
The haploid selection model accounts for the increase of the 'Delta' & 'Omicron' variants of the Covid-19 RNA virus. Whereas the example above describes a selective advantage in vitro, first the Delta and now the Omicron variants are at a selective advantage in vivo because of its higher infectivity rate (Ro, read as "R nought") relative to the original strain.
Figure © 2013 by Sinauer; Text material © 2022 by Steven M. Carr