Author:
CHARLESWORTH BRIAN,CHARLESWORTH DEBORAH
Abstract
Theoretical arguments are presented which suggest that each advance
of Muller's ratchet in a
haploid asexual population causes the fixation of a deleterious
mutation at a single locus. A
similar process operates in a diploid, fully asexual population under a
wide range of parameter
values, with respect to fixation within one of the two haploid genomes.
Fixations of deleterious
mutations in asexual species can thus be greatly accelerated in comparison
with a freely recombining
genome, if the ratchet is operating. In a diploid with segregation of a
single chromosome, but no
crossing over within the chromosome, the advance of the ratchet can be
decoupled
from fixation if
mutations are sufficiently close to recessivity. A new analytical approximation
for the rate of
advance of the ratchet is proposed. Simulation results are presented that
validate the assertions
about fixation. The simulations show that none of the analytical approximations
for the rate of
advance of the ratchet are satisfactory when population size is large.
The relevance of these results
for evolutionary processes such as Y chromosome degeneration is discussed.
Subject
Genetics,General Medicine
Cited by
145 articles.
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