scholarly journals THE IMPACT OF RANDOM AND LINEAL FISSION ON THE GENETIC DIVERGENCE OF SMALL HUMAN GROUPS: A CASE STUDY AMONG THE YANOMAMA

Genetics ◽  
1981 ◽  
Vol 98 (1) ◽  
pp. 179-197
Author(s):  
Peter E Smouse ◽  
Virginia J Vitzthum ◽  
James V Neel
Keyword(s):  
Gene Flow ◽  
Genetic Divergence ◽  
Homo Sapiens ◽  
Biological Evolution ◽  
Finite Size ◽  
Fission Products ◽  
Basic Unit ◽  
Effective Population ◽  
Random Assortment ◽  
The Impact

ABSTRACT Most of the genetic divergence that currently separates populations of Homo sapiens must have arisen during that long period when the local village (or band) was the basic unit of biological evolution. Studies of tribally intact Amerindian groups exhibiting such small-group organization have demonstrated marked genetic divergence between nearby villages. Some of this genetic radiation can be attributed to the effects of random genetic drift over time within these small demes. Some of it, however, might be better ascribed to the consequences of nonrandom genetic assortment at the time of village fission, a recurring event for such groups. Even random genetic assortment at the time of fission would lead to some genetic divergence, due to the finite size of the parent gene pool. We term the genetic consequences of random assortment the random fission effect. Routinely, village fission occurs along family lines, leading to even greater genetic divergence between the daughter villages. We use the term lineal fission effect to describe the genetic consequences of nonrandom assortment and contrast these results with those derived from random assortment.——A formal treatment of random and lineal fission effects is developed, first for the single-locus case, then for the multiple-locus extension. Using this formulation, three Yanomama fission events were examined. Fission in the Yanomama often involves a great deal of mutual hostility between the two factions, so that subsequent gene flow between the two daughter villages is minimal. The first two examples are typical of the Yanomama behavior norm, and are accompanied by a minimum of subsequent gene flow between the daughter villages. In these two cases, the observed divergence values are very large and are also very unlikely under random fission. The lineal fission effect is pronounced. The net impact of lineal fission is to reduce the effective size of the village at the time of fission by a factor of four, relative to expectation from random fission. The third example, however, involved an unusually amicable split of a village, followed by free genetic exchange between the fission products. This "friendly fission" yields an observed divergence value not much in excess of the expectation from random fission.—The long-term consequences of such fission bottlenecks in effective population size are discussed for both intra- and inter-tribal genetic diversity. It appears that the rate of genetic divergence for tribal and subtribal groups may have been somewhat greater than would be expected from classical drift arguments.

Inferring population connectivity across the range of the purple-crowned fairy-wren (Malurus coronatus) from mitochondrial DNA and morphology: implications for conservation management

2012 ◽  
Vol 60 (3) ◽  
pp. 199 ◽  
Author(s):  
Anja Skroblin ◽  
Robert Lanfear ◽  
Andrew Cockburn ◽  
Sarah Legge
Keyword(s):  
Mitochondrial Dna ◽  
Gene Flow ◽  
Dna Sequences ◽  
Genetic Divergence ◽  
Conservation Management ◽  
Habitat Degradation ◽  
Morphological Difference ◽  
Population Connectivity ◽  
Isolated Populations ◽  
The Impact

Knowledge of population structure and patterns of connectivity is required to implement effective conservation measures for the purple-crowned fairy-wren (Malurus coronatus), a threatened endemic of northern Australia. This study aimed to identify barriers to dispersal across the distribution of M. coronatus, investigate the impact that the recent declines may have on population connectivity, and propose conservation actions to maintain natural patterns of gene flow. Analysis of mitochondrial DNA sequences from 87 M. coronatus identified two phylogenetic clusters that corresponded with the phenotypically defined western (M. c. coronatus) and eastern (M. c. macgillivrayi) subspecies. The genetic divergence between these subspecies was consistent with isolation by a natural barrier to gene flow, and supports their separate conservation management. Within the declining M. c. coronatus, the lack of genetic divergence and only slight morphological difference between remnant populations indicates that populations were recently linked by gene flow. It is likely that widespread habitat degradation and the recent extirpation of M. c. coronatus from the Ord River will disrupt connectivity between, and dynamics within, remnant populations. To prevent further declines, conservation of M. coronatus must preserve areas of quality habitat and restore connectivity between isolated populations.

scholarly journals Long-term ‘islands’ in the landscape: low gene flow, effective population size and genetic divergence in the shrubHakea oldfieldii(Proteaceae)

2015 ◽  
Vol 179 (2) ◽  
pp. 319-334 ◽  
Author(s):  
Jane F. Sampson ◽  
Maggie Hankinson ◽  
Shelley McArthur ◽  
Sarah Tapper ◽  
Margaret Langley ◽  
...  
Keyword(s):  
Gene Flow ◽  
Population Size ◽  
Effective Population Size ◽  
Genetic Divergence ◽  
Effective Population

Defining spatial genetic structure and management units for vulnerable koala (Phascolarctos cinereus) populations in the Sydney region, Australia

2010 ◽  
Vol 37 (2) ◽  
pp. 156 ◽  
Author(s):  
Tristan Lee ◽  
Kyall R. Zenger ◽  
Robert L. Close ◽  
Marilyn Jones ◽  
David N. Phalen
Keyword(s):  
Gene Flow ◽  
Population Size ◽  
Spatial Genetic Structure ◽  
Effective Population ◽  
Management Units ◽  
Study Region ◽  
Phascolarctos Cinereus ◽  
Fragmented Habitat ◽  
Military Reserve ◽  
The Impact

Context. Mammal populations around the world are increasingly threatened with population fragmentation because of loss of habitat or barriers to gene flow. The investigation of koala populations in the Sydney region not only provides valuable information about this vulnerable species, but also serves as a model for other species that have suffered major rapid declines in population size, and are now recovering in fragmented habitat. The peri-urban study region allows investigation of the impact of landscape features such as major roads and housing developments on koala gene flow. Aims. Animals originating from four geographic sampling areas around Sydney, New South Wales, Australia, were examined to determine population structure and gene flow and to identify barriers to gene flow and management units. Methods. The present study examined 12 microsatellite loci and used Bayesian assignment methods and genic frequency analysis methods to identify demographically separate populations and barriers to gene flow between those populations. Key results. Three discrete populations were resolved, with all displaying moderate to high levels of genetic differentiation among them (θ = 0.141–0.224). The allelic richness and heterozygosity of the Blue Mountains population (A = 6.46, HO = 0.66) is comparable to the highest diversity found in any koala population previously investigated. However, considerably lower genetic diversity was found in the Campbelltown population (A = 3.17, HO = 0.49), which also displayed evidence of a recent population bottleneck (effective population size estimated at 16–21). Conclusions. Animals separated by a military reserve were identified as one population, suggesting that the reserve maintains gene flow within this population. By contrast, strong differentiation of two geographically close populations separated by several potential barriers to gene flow suggested these land-use features pose barriers to gene flow. Implications. Implications of these findings for management of koala populations in the Greater Sydney region are discussed. In particular, the need to carefully consider the future of a military reserve is highlighted, along with possible solutions to allow gene flow across the proposed barrier regions. Because these are demographically separate populations, specific management plans tailored to the needs of each population will need to be formulated.

scholarly journals Trends in genetic diversity and the effect of inbreeding in American Angus cattle under genomic selection

2021 ◽  
Vol 53 (1) ◽  
Author(s):  
Emmanuel A. Lozada-Soto ◽  
Christian Maltecca ◽  
Duc Lu ◽  
Stephen Miller ◽  
John B. Cole ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Beef Cattle ◽  
Genomic Selection ◽  
Inbreeding Depression ◽  
Growth Traits ◽  
Effective Population ◽  
Angus Cattle ◽  
Genomic Inbreeding ◽  
Chromosome Segments ◽  
The Impact

Abstract Background While the adoption of genomic evaluations in livestock has increased genetic gain rates, its effects on genetic diversity and accumulation of inbreeding have raised concerns in cattle populations. Increased inbreeding may affect fitness and decrease the mean performance for economically important traits, such as fertility and growth in beef cattle, with the age of inbreeding having a possible effect on the magnitude of inbreeding depression. The purpose of this study was to determine changes in genetic diversity as a result of the implementation of genomic selection in Angus cattle and quantify potential inbreeding depression effects of total pedigree and genomic inbreeding, and also to investigate the impact of recent and ancient inbreeding. Results We found that the yearly rate of inbreeding accumulation remained similar in sires and decreased significantly in dams since the implementation of genomic selection. Other measures such as effective population size and the effective number of chromosome segments show little evidence of a detrimental effect of using genomic selection strategies on the genetic diversity of beef cattle. We also quantified pedigree and genomic inbreeding depression for fertility and growth. While inbreeding did not affect fertility, an increase in pedigree or genomic inbreeding was associated with decreased birth weight, weaning weight, and post-weaning gain in both sexes. We also measured the impact of the age of inbreeding and found that recent inbreeding had a larger depressive effect on growth than ancient inbreeding. Conclusions In this study, we sought to quantify and understand the possible consequences of genomic selection on the genetic diversity of American Angus cattle. In both sires and dams, we found that, generally, genomic selection resulted in decreased rates of pedigree and genomic inbreeding accumulation and increased or sustained effective population sizes and number of independently segregating chromosome segments. We also found significant depressive effects of inbreeding accumulation on economically important growth traits, particularly with genomic and recent inbreeding.

scholarly journals Nonlocal and Size-Dependent Dielectric Function for Plasmonic Nanoparticles

2019 ◽  
Vol 9 (15) ◽  
pp. 3083
Author(s):  
Kai-Jian Huang ◽  
Shui-Jie Qin ◽  
Zheng-Ping Zhang ◽  
Zhao Ding ◽  
Zhong-Chen Bai
Keyword(s):  
Metallic Nanoparticles ◽  
High Efficiency ◽  
Finite Size ◽  
Plasmonic Nanostructures ◽  
Accurate Analysis ◽  
Finite Size Effects ◽  
Size Dependent ◽  
Quantum Size ◽  
The Impact ◽  
Electron Energy Loss

We develop a theoretical approach to investigate the impact that nonlocal and finite-size effects have on the dielectric response of plasmonic nanostructures. Through simulations, comprehensive comparisons of the electron energy loss spectroscopy (EELS) and the optical performance are discussed for a gold spherical dimer system in terms of different dielectric models. Our study offers a paradigm of high efficiency compatible dielectric theoretical framework for accounting the metallic nanoparticles behavior combining local, nonlocal and size-dependent effects in broader energy and size ranges. The results of accurate analysis and simulation for these effects unveil the weight and the evolution of both surface and bulk plasmons vibrational mechanisms, which are important for further understanding the electrodynamics properties of structures at the nanoscale. Particularly, our method can be extended to other plasmonic nanostructures where quantum-size or strongly interacting effects are likely to play an important role.

scholarly journals The influence of physical parameters on the in-situ metal carbonyl complex formation studied with the Fast On-line Reaction Apparatus (FORA)

2021 ◽  
Vol 109 (4) ◽  
pp. 261-281
Author(s):  
Yves Wittwer ◽  
Robert Eichler ◽  
Dominik Herrmann ◽  
Andreas Türler
Keyword(s):  
Gas Flow ◽  
Metal Carbonyl ◽  
Fission Products ◽  
Reaction Chamber ◽  
Single Atom ◽  
Physical Parameters ◽  
Carbonyl Complex ◽  
Reaction Conditions ◽  
On Line ◽  
The Impact

Abstract The Fast On-line Reaction Apparatus (FORA) was used to investigate the influence of various reaction parameters onto the formation and transport of metal carbonyl complexes (MCCs) under single-atom chemistry conditions. FORA is based on a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes. Those are recoiling from the spontaneous fission source into a reaction chamber flushed with a gas-mixture containing CO. Upon contact with CO, fission products form volatile MCCs which are further transported by the gas stream to the detection setup, consisting of a charcoal trap mounted in front of a HPGe γ-detector. Depending on the reaction conditions, MCCs are formed and transported with different efficiencies. Using this setup, the impact of varying physical parameters like gas flow, gas pressure, kinetic energy of fission products upon entering the reaction chamber and temperature of the reaction chamber on the formation and transport yields of MCCs was investigated. Using a setup similar to FORA called Miss Piggy, various gas mixtures of CO with a selection of noble gases, as well as N2 and H2, were investigated with respect to their effect onto MCC formation and transport. Based on this measurements, optimized reaction conditions to maximize the synthesis and transport of MCCs are suggested. Explanations for the observed results supported by simulations are suggested as well.

Synthetic Riboswitches for the Analysis of tRNA Processing by eukaryotic RNase P Enzymes

RNA ◽  
2022 ◽  
pp. rna.078814.121
Author(s):  
Anna Ender ◽  
Nadine Grafl ◽  
Tim Kolberg ◽  
Sven Findeiss ◽  
Peter F. Stadler ◽  
...  
Keyword(s):  
Homo Sapiens ◽  
Rnase P ◽  
Single Stranded Region ◽  
Domains Of Life ◽  
The Individual ◽  
The Impact ◽  
Individual Enzyme ◽  
Trna Precursor

Removal of the 5' leader region is an essential step in the maturation of tRNA molecules in all domains of life. This reaction is catalyzed by various RNase P activities, ranging from ribonucleoproteins with ribozyme activity to protein-only forms. In Escherichia coli, the efficiency of RNase P mediated cleavage can be controlled by computationally designed riboswitch elements in a ligand-dependent way, where the 5' leader sequence of a tRNA precursor is either sequestered in a hairpin structure or presented as a single-stranded region accessible for maturation. In the presented work, the regulatory potential of such artificial constructs is tested on different forms of eukaryotic RNase P enzymes – two protein-only RNase P enzymes (PRORP1 and PRORP2) from Arabidopsis thaliana and the ribonucleoprotein of Homo sapiens. The PRORP enzymes were analyzed in vitro as well as in vivo in a bacterial RNase P complementation system. We also tested in HEK293T cells whether the riboswitches remain functional with human nuclear RNase P. While the regulatory principle of the synthetic riboswitches applies for all tested RNase P enzymes, the results also show differences in the substrate requirements of the individual enzyme versions. Hence, such designed RNase P riboswitches represent a novel tool to investigate the impact of the structural composition of the 5'-leader on substrate recognition by different types of RNase P enzymes.

Investigation of Fuel Burnup Impacts on Nuclear Reactor Safety Parameters in the Canadian Pressure Tube Supercritical Water-Cool Reactor

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Ahmad Moghrabi ◽  
David Raymond Novog
Keyword(s):  
Nuclear Reactor ◽  
High Efficiency ◽  
Fission Products ◽  
Neutron Cross Section ◽  
Fuel Mixture ◽  
Pressure Tube ◽  
Candu Reactors ◽  
Safety Parameters ◽  
Nuclear Reactor Safety ◽  
The Impact

The Canadian pressure-tube super critical water-cooled reactor (PT-SCWR) is an advanced generation IV reactor concept which is considered as an evolution of the conventional Canada Deuterium Uranium (CANDU) reactor that includes both pressure tubes and a low temperature and pressure heavy water moderator. The Canadian PT-SCWR fuel assembly utilizes a plutonium and thorium fuel mixture with supercritical light water coolant flowing through the high-efficiency re-entrance channel (HERC). In this work, the impact of fuel depletion on the evolution of lattice physics phenomena was investigated starting from fresh fuel to burnup conditions (25 MW d kg−1 [HM]) through sensitivity and uncertainty analyses using the lattice physics modules in standardized computer analysis for licensing evaluation (SCALE). Given the evolution of key phenomena such as void reactivity in traditional CANDU reactors with burnup, this study focuses on the impact of fission products, 233U breeding, and minor actinides on fuel performance. The work shows that the most significant change in fuel properties with burnup is the depletion of fission isotopes of Pu and the buildup of high-neutron cross section fission products, resulting in a decrease in cell k∞ with burnup as expected. Other impacts such as the presence of protactinium and uranium-233 are also discussed. When the feedback coefficients are assessed in terms of reactivity, there is considerable variation as a function of fuel depletion; however, when assessed as Δk (without normalization to the reference reactivity which changes with burnup), the net changes are almost invariant with depletion.

scholarly journals Localisation determines the optimal noise rate for quantum transport

2021 ◽  
Author(s):  
Alexandre Coates ◽  
Brendon W Lovett ◽  
Erik Gauger
Keyword(s):  
Energy Transport ◽  
Optimal Transport ◽  
Detailed Balance ◽  
Finite Size ◽  
Temperature Limit ◽  
Transport Efficiency ◽  
Size Dependent ◽  
Noise Rate ◽  
Pure Dephasing ◽  
The Impact

Abstract Environmental noise plays a key role in determining the efficiency of transport in quantum systems. However, disorder and localisation alter the impact of such noise on energy transport. To provide a deeper understanding of this relationship we perform a systematic study of the connection between eigenstate localisation and the optimal dephasing rate in 1D chains. The effects of energy gradients and disorder on chains of various lengths are evaluated and we demonstrate how optimal transport efficiency is determined by both size-independent, as well as size-dependent factors. By discussing how size-dependent influences emerge from finite size effects we establish when these effects are suppressed, and show that a simple power law captures the interplay between size-dependent and size-independent responses. Moving beyond phenomenological pure dephasing, we implement a finite temperature Bloch-Redfield model that captures detailed balance. We show that the relationship between localisation and optimal environmental coupling strength continues to apply at intermediate and high temperature but breaks down in the low temperature limit.

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