scholarly journals Sign of selection on mutation rate modifiers depends on population size

2017 ◽  
Author(s):  
Yevgeniy Raynes ◽  
C. Scott Wylie ◽  
Paul D. Sniegowski ◽  
Daniel M. Weinreich
Keyword(s):  
Population Size ◽  
Mutation Rate ◽  
Critical Role ◽  
Genetic System ◽  
Indirect Selection ◽  
Fitness Effects ◽  
Sign Inversion ◽  
Large Populations ◽  
Laboratory Populations

SummaryThe influence of population size (N) on natural selection acting on alleles that affect fitness has been understood for over half a century1. As N declines, genetic drift overwhelms selection and alleles with direct fitness effects are rendered neutral. Often, though, alleles experience so called indirect selection, meaning they affect not the fitness of an individual but the fitness distribution of its offspring. Some of the best studied examples of indirect selection include alleles that modify aspects of the genetic system such as recombination2 and mutation3 rates. Here we use analytics, simulations and experimental populations of S. cerevisiae to show that modifiers that increase the genomic mutation rate (mutators) are favored by indirect selection in large populations but become disfavored as N declines. This surprising phenomenon of sign inversion in selective effect demonstrates that indirect selection on a mutator exhibits a qualitatively novel dependence on N. Sign inversion may help understand the relatively sporadic distribution of mutators in nature despite their frequent emergence in laboratory populations. More generally, sign inversion may be broadly applicable to other instances of indirect selection, suggesting a previously unappreciated but critical role of population size in evolution.

scholarly journals Sign of selection on mutation rate modifiers depends on population size

2018 ◽  
Vol 115 (13) ◽  
pp. 3422-3427 ◽  
Author(s):  
Yevgeniy Raynes ◽  
C. Scott Wylie ◽  
Paul D. Sniegowski ◽  
Daniel M. Weinreich
Keyword(s):  
Population Size ◽  
Mutation Rate ◽  
Genetic System ◽  
Indirect Selection ◽  
Mutation Rates ◽  
Deleterious Mutations ◽  
Fitness Effects ◽  
Sign Inversion ◽  
Large Populations ◽  
The Cost

The influence of population size (N) on natural selection acting on alleles that affect fitness has been understood for almost a century. AsNdeclines, genetic drift overwhelms selection and alleles with direct fitness effects are rendered neutral. Often, however, alleles experience so-called indirect selection, meaning they affect not the fitness of an individual but the fitness distribution of its offspring. Some of the best-studied examples of indirect selection include alleles that modify aspects of the genetic system such as recombination and mutation rates. Here, we use analytics, simulations, and experimental populations ofSaccharomyces cerevisiaeto examine the influence ofNon indirect selection acting on alleles that increase the genomic mutation rate (mutators). Mutators experience indirect selection via genomic associations with beneficial and deleterious mutations they generate. We show that, asNdeclines, indirect selection driven by linked beneficial mutations is overpowered by drift before drift can neutralize the cost of the deleterious load. As a result, mutators transition from being favored by indirect selection in large populations to being disfavored asNdeclines. This surprising phenomenon of sign inversion in selective effect demonstrates that indirect selection on mutators exhibits a profound and qualitatively distinct dependence onN.

scholarly journals Sign inversion in selection on ploidy

2021 ◽  
Author(s):  
Yevgeniy Raynes ◽  
Daniel M Weinreich
Keyword(s):  
Population Size ◽  
Natural World ◽  
Indirect Selection ◽  
Beneficial Mutations ◽  
Agent Based ◽  
Sign Inversion ◽  
Large Populations ◽  
A Cell ◽  
Asexual Populations ◽  
The Cost

Ploidy - the number of homologous chromosome sets in a cell - is remarkably variable across the natural world, yet the evolutionary processes that have resulted in such diversity remain poorly understood. Here we use stochastic agent-based simulations to model ploidy evolution under the influence of indirect selection, i.e., selection mediated solely by statistical associations with fitness-affecting mutations. We find that in non-equilibrium asexual populations, the sign of selection on ploidy can change with population size - a phenomenon we have previously termed sign inversion. In large populations, ploidy dynamics are dominated by indirect effects of selection on beneficial mutations, which favors haploids over diploids. However, as population size declines, selection for beneficial mutations is neutralized by random genetic drift before drift can overwhelm selection against the cost of the deleterious mutational load. As a result, in small populations indirect selection is dominated by the cost of the deleterious load, which favors diploids over haploids. Our work adds to the growing body of evidence challenging established evolutionary theory that population size can affect only the efficiency, but not the sign, of natural selection.

scholarly journals Population Density or Populations Size. Which Factor Determines Urban Traffic Congestion?

2021 ◽  
Vol 13 (8) ◽  
pp. 4280
Author(s):  
Yu Sang Chang ◽  
Sung Jun Jo ◽  
Yoo-Taek Lee ◽  
Yoonji Lee
Keyword(s):  
Population Density ◽  
Population Size ◽  
Traffic Congestion ◽  
Critical Role ◽  
Small Population ◽  
High Density ◽  
Urban Traffic ◽  
Contradictory Result ◽  
Low Density

A large number of articles have documented that as population density of cities increases, car use declines and public transit use rises. These articles had a significant impact of promoting high-density compact urban development to mitigate traffic congestion. Another approach followed by other researchers used the urban scaling model to indicate that traffic congestion increases as population size of cities increases, thus generating a possible contradictory result. Therefore, this study examines the role of both density and population size on traffic congestion in 164 global cities by the use of Stochastic Impacts by Regression on Population, Affluence and Technology model. We divide 164 cities into the two subgroups of 66 low density cities and 98 high density cities for analysis. The findings from the subgroups analysis indicated a clear-cut difference on the critical role of density in low-density cities and the exclusive role of population size in high-density cities. Furthermore, using threshold regression model, 164 cities are divided into the two regions of large and small population cities to determine population scale advantage of traffic congestion. Our findings highlight the importance of including analysis of subgroups based on density and/or population size in future studies of traffic congestion.

scholarly journals Population size mediates the contribution of high-rate and large-benefit mutations to parallel evolution

2021 ◽  
Author(s):  
Martijn F. Schenk ◽  
Mark P. Zwart ◽  
Sungmin Hwang ◽  
Philip Ruelens ◽  
Edouard Severing ◽  
...  
Keyword(s):  
Population Size ◽  
Parallel Evolution ◽  
Point Mutations ◽  
High Rate ◽  
Structural Variants ◽  
Bacterial Populations ◽  
Fitness Effects ◽  
Different Types ◽  
Large Benefit

Both mutations with large benefits and mutations occurring at high rates may cause parallel evolution, but their contribution is expected to depend on population size. We show that small and large bacterial populations adapt to a novel antibiotic using similar numbers, but different types of mutations. Small populations repeatedly substitute similar high-rate structural variants, including the deletion of a nonfunctional β-lactamase, and evolve modest resistance levels. Hundred-fold larger populations more frequently use the same low-rate, large-benefit point mutations, including those activating the β-lactamase, and reach 50-fold higher resistance levels. Our results demonstrate a key role of clonal interference in mediating the contribution of high-rate and large-benefit mutations in populations of different size, facilitated by a tradeoff between rates and fitness effects of different mutation classes.

scholarly journals Low genetic variation is associated with low mutation rate in the giant duckweed

2018 ◽  
Author(s):  
Shuqing Xu ◽  
Jessica Stapley ◽  
Saskia Gablenz ◽  
Justin Boyer ◽  
Klaus J. Appenroth ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Mutation Rate ◽  
Spontaneous Mutation ◽  
Effective Population ◽  
Spontaneous Mutation Rate ◽  
Low Genetic Diversity ◽  
Genome Wide ◽  
Census Population Size

AbstractMutation rate and effective population size (Ne) jointly determine intraspecific genetic diversity, but the role of mutation rate is often ignored. We investigate genetic diversity, spontaneous mutation rate andNein the giant duckweed (Spirodela polyrhiza). Despite its large census population size, whole-genome sequencing of 68 globally sampled individuals revealed extremely low within-species genetic diversity. Assessed under natural conditions, the genome-wide spontaneous mutation rate is at least seven times lower than estimates made for other multicellular eukaryotes, whereasNeis large. These results demonstrate that low genetic diversity can be associated with large-Nespecies, where selection can reduce mutation rates to very low levels, and accurate estimates of mutation rate can help to explain seemingly counterintuitive patterns of genome-wide variation.One Sentence SummaryThe low-down on a tiny plant: extremely low genetic diversity in an aquatic plant is associated with its exceptionally low mutation rate.

THE ROLE OF MUTATION AND POPULATION SIZE IN GENETIC ALGORITHMS APPLIED TO PHYSICS PROBLEMS

2001 ◽  
Vol 12 (09) ◽  
pp. 1345-1355 ◽  
Author(s):  
E. BELMONT-MORENO
Keyword(s):  
Genetic Algorithm ◽  
Genetic Algorithms ◽  
Population Size ◽  
Mutation Rate ◽  
Test Problems ◽  
Optimum Performance ◽  
Analytical Expressions ◽  
Standard Genetic Algorithm ◽  
Physics Problems

A standard Genetic Algorithm is applied to a set of test problems, three of them taken from physics and the rest analytical expressions explicitly constructed to test search procedures. The relation between mutation rate and population size in the search for optimum performance is obtained showing similar behavior in these problems.

scholarly journals Evolution of Mutation Rate in Astronomically Large Phytoplankton Populations

2020 ◽  
Vol 12 (7) ◽  
pp. 1051-1059
Author(s):  
Marc Krasovec ◽  
Rosalind E M Rickaby ◽  
Dmitry A Filatov
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Mutation Rate ◽  
Spontaneous Mutation ◽  
Large Population ◽  
Marine Phytoplankton ◽  
Mutation Rates ◽  
Effective Population ◽  
Spontaneous Mutation Rate ◽  
Large Populations

Abstract Genetic diversity is expected to be proportional to population size, yet, there is a well-known, but unexplained lack of genetic diversity in large populations—the “Lewontin’s paradox.” Larger populations are expected to evolve lower mutation rates, which may help to explain this paradox. Here, we test this conjecture by measuring the spontaneous mutation rate in a ubiquitous unicellular marine phytoplankton species Emiliania huxleyi (Haptophyta) that has modest genetic diversity despite an astronomically large population size. Genome sequencing of E. huxleyi mutation accumulation lines revealed 455 mutations, with an unusual GC-biased mutation spectrum. This yielded an estimate of the per site mutation rate µ = 5.55×10−10 (CI 95%: 5.05×10−10 – 6.09×10−10), which corresponds to an effective population size Ne ∼ 2.7×106. Such a modest Ne is surprising for a ubiquitous and abundant species that accounts for up to 10% of global primary productivity in the oceans. Our results indicate that even exceptionally large populations do not evolve mutation rates lower than ∼10−10 per nucleotide per cell division. Consequently, the extreme disparity between modest genetic diversity and astronomically large population size in the plankton species cannot be explained by an unusually low mutation rate.

MECHANISM OF EMERGENCE OF RESISTANCE TO STREPTOMYCIN OF H. PERTUSSIS AND H. PARAPERTUSSIS DURING TREATMENT WITH THIS ANTIBIOTIC

PEDIATRICS ◽  
1949 ◽  
Vol 4 (4) ◽  
pp. 461-467
Author(s):  
HATTIE E. ALEXANDER ◽  
WINIFRED REDMAN
Keyword(s):  
Population Size ◽  
Mutation Rate ◽  
Mutation Frequency ◽  
Large Populations ◽  
Emergence Of Resistance ◽  
Resistant Trait ◽  
Resistant Cells

In large populations of H. pertussis and H. parapertussis which have never been exposed to streptomycin, it is possible to demonstrate the presence of cells resistant to streptomycin 1000 mcg./cc. These highly resistant cells exhibit the following traits which are characteristic of mutants: 1. Irregular occurrence in different independent cultures of same population size and strain and therefore independence of the action of streptomycin. 2. Transmission of the resistant trait unchanged in degree through many subcultures in the absence of streptomycin and, therefore, inheritance of the trait. 3. A rate of occurrence consistent with mutation frequency; the mutation rate of cells resistant to 1000 mcg./cc. does not differ significantly between these two species.

The Role of the SLP in Autism Spectrum Disorder Screening and Assessment

2008 ◽  
Vol 15 (2) ◽  
pp. 50-59 ◽  
Author(s):  
Amy Philofsky
Keyword(s):  
Language Development ◽  
Critical Role ◽  
Children With Autism ◽  
Autism Spectrum ◽  
Children With Asd ◽  
Prevalence Estimates ◽  
Notable Increase ◽  
Screening Assessment ◽  
Critical Components

AbstractRecent prevalence estimates for autism have been alarming as a function of the notable increase. Speech-language pathologists play a critical role in screening, assessment and intervention for children with autism. This article reviews signs that may be indicative of autism at different stages of language development, and discusses the importance of several psychometric properties—sensitivity and specificity—in utilizing screening measures for children with autism. Critical components of assessment for children with autism are reviewed. This article concludes with examples of intervention targets for children with ASD at various levels of language development.

A critical role of iNOS-derived Nitric Oxide (NO) and progesterone in implantation

1998 ◽  
Vol 5 (1) ◽  
pp. 115A-115A
Author(s):  
K CHWALISZ ◽  
E WINTERHAGER ◽  
T THIENEL ◽  
R GARFIELD
Keyword(s):  
Nitric Oxide ◽  
Critical Role
Sign in / Sign up

Export Citation Format

Share Document