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DTSTAMP:20260814T101255Z
LAST-MODIFIED:-11130T050000Z
DTSTART:20111130T180000Z
DTEND:20111130T190000Z
UID:event386@bu.edu
URL:http://physics.bu.edu/internal/events/show/386
SUMMARY:Dynamic mutation selection balance as an evolutionary attractor
DESCRIPTION:Featuring Sidhartha Goyal\, KITP at UCSB\nHosted by: Pankaj Meh
	ta\n\nPart of the Condensed Matter Theory Seminar Series.\n\nAbstract: The 
	vast majority of mutations are deleterious\, and areeliminated by purifying
	 selection. Yet in finite asexual populations\,purifying selection cannot c
	ompletely prevent the accumulation ofdeleterious mutations due to Muller's 
	ratchet: once lost by stochasticdrift\, the most-fit class of genotypes is 
	lost forever. If deleteriousmutations are weakly selected\, Muller's ratche
	t turns into amutational ``meltdown'' leading to a rapid degradation of pop
	ulationfitness. Evidently\, the long term stability of an asexual populatio
	nrequires an influx of beneficial mutations that continuouslycompensate for
	 the accumulation of the weakly deleterious ones. Herewe propose that the s
	table evolutionary state of a population in astatic environment is a dynami
	c mutation-selection balance\, whereaccumulation of deleterious mutations i
	s on average offset by theinflux of beneficial mutations. We argue that thi
	s state exists forany population size $N$ and mutation rate $U$.  Assuming 
	thatbeneficial and deleterious mutations have the same fitness effect$\ss$\
	, we calculate the fraction of beneficial mutations\, $\e$\, thatmaintains 
	the balanced state. We find that a surprisingly low $\e$suffices to maintai
	n stability\, even in small populations in the faceof high mutation rates a
	nd weak selection.  This may explain themaintenance of mitochondria and oth
	er asexual genomes\, and hasimplications for the expected statistics of gen
	etic diversity in thesepopulations.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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