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Abstract: A variety of genome transformations can occur as a microbial populationadapts to a large environmental change. In particular, genomic surveys indicatethat, following the transition to an obligate, host-dependent symbiont, thedensity of transposons first rises, then subsequently declines overevolutionary time. Here, we show that these observations can be accounted forby a class of generic stochastic models for the evolution of genomes in thepresence of continuous selection and gene duplication. The models use a fitnessfunction that allows for partial contributions from multiple gene copies, is anincreasing but bounded function of copy number, and is optimal for one fullyadapted gene copy. We use Monte Carlo simulation to show that the dynamicsresult in an initial rise in gene copy number followed by a subsequent fall dueto adaptation to the new environmental parameters. These results are robust forreasonable gene duplication and mutation parameters when adapting to a noveltarget sequence. Our model provides a generic explanation for the dynamics ofmicrobial transposon density following a large environmental changes such ashost restriction.



Author: Nicholas Chia, Nigel Goldenfeld

Source: https://arxiv.org/







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