scholarly journals Recombination Disequilibrium in Ideal and Natural Populations

2015 ◽  
Author(s):  
Yuan-De Tan
Keyword(s):  
Random Mating ◽  
Natural Populations ◽  
Population History ◽  
Human Populations ◽  
Linkage Maps ◽  
Multiple Loci ◽  
Breeding Populations ◽  
Mating Population ◽  
History Of ◽  
Population Recombination

Following Hardy-Weinberg disequilibrium (HWD) occurring at a single locus and linkage disequilibrium (LD) between two loci in generations, we here proposed the third genetic disequilibrium in population: recombination disequilibrium (RD). RD is a measurement of crossover interference among multiple loci in a random mating population. In natural populations besides recombination interference, RD may also be due to selection, mutation, gene conversion, drift and/or migration. Therefore, similarly to LD, RD will also reflect the history of natural selection and mutation. In breeding populations, RD purely results from recombination interference and hence can be used to build or evaluate and correct a linkage map. Several practical examples from F2, testcross and human populations indeed demonstrate that RD is useful for measuring recombination interference between two short intervals and evaluating linkage maps. As with LD, RD will be important for studying genetic mapping, association of haplotypes with disease, plant breading and population history.

scholarly journals Insights into human genetic variation and population history from 929 diverse genomes

2019 ◽  
Author(s):  
Anders Bergström ◽  
Shane A. McCarthy ◽  
Ruoyun Hui ◽  
Mohamed A. Almarri ◽  
Qasim Ayub ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Central Africa ◽  
Population History ◽  
Human Populations ◽  
Genome Sequences ◽  
High Coverage ◽  
Geographical Regions ◽  
History Of ◽  
Different Populations ◽  
Source Populations

AbstractGenome sequences from diverse human groups are needed to understand the structure of genetic variation in our species and the history of, and relationships between, different populations. We present 929 high-coverage genome sequences from 54 diverse human populations, 26 of which are physically phased using linked-read sequencing. Analyses of these genomes reveal an excess of previously undocumented private genetic variation in southern and central Africa and in Oceania and the Americas, but an absence of fixed, private variants between major geographical regions. We also find deep and gradual population separations within Africa, contrasting population size histories between hunter-gatherer and agriculturalist groups in the last 10,000 years, a potentially major population growth episode after the peopling of the Americas, and a contrast between single Neanderthal but multiple Denisovan source populations contributing to present-day human populations. We also demonstrate benefits to the study of population relationships of genome sequences over ascertained array genotypes. These genome sequences are freely available as a resource with no access or analysis restrictions.

scholarly journals Whales and Men: genetic inferences uncover a detailed history of hunting in bowhead whale

2020 ◽  
Author(s):  
TB Hoareau
Keyword(s):  
Population Change ◽  
Natural Populations ◽  
Late Glacial ◽  
Population History ◽  
Bowhead Whale ◽  
The Arctic ◽  
Arctic Seas ◽  
The North ◽  
Time Calibration ◽  
History Of

AbstractAfter millennia of hunting and a population collapse, it is still challenging to understand the genetic consequences of whaling on the circumarctic bowhead whale. Here I use published modern mtDNA sequences from the Bering-Chukchi-Beaufort population and a new time calibration to show that late–glacial climate changes and whaling have been the major drivers of population change. Cultures that hunted in the Arctic Seas from as early as 5000 years ago appear to be responsible for successive declines of the population growth, bringing the effective size down to 38% of its pristine population size. The Thules and the Basques (year 1000–1730) who only hunted in the North Atlantic had a major impact on this North Pacific population, indicating that bowhead whale stocks respond to harvesting as a single population unit. Recent positive growth is inferred only after the end of commercial whaling in 1915, and for levels of harvesting that are close to the current annual quota of 67 whales. By unfolding the population history of the bowhead whale, I provide compelling evidence that mtDNA yields critical yet undervalued information for management and conservation of natural populations.

scholarly journals Introgression makes waves in inferred histories of effective population size

2017 ◽  
Author(s):  
John Hawks
Keyword(s):  
Gene Flow ◽  
Population Size ◽  
Effective Population Size ◽  
Population History ◽  
Human Populations ◽  
Effective Population ◽  
History Of ◽  
Or Gene ◽  
Time Of Origin ◽  
Past Population

AbstractHuman populations have a complex history of introgression and of changing population size. Human genetic variation has been affected by both these processes, so that inference of past population size depends upon the pattern of gene flow and introgression among past populations. One remarkable aspect of human population history as inferred from genetics is a consistent “wave” of larger effective population size, prior to the bottlenecks and expansions of the last 100,000 years. Here I carry out a series of simulations to investigate how introgression and gene flow from genetically divergent ancestral populations affect the inference of ancestral effective population size. Both introgression and gene flow from an extinct, genetically divergent population consistently produce a wave in the history of inferred effective population size. The time and amplitude of the wave reflect the time of origin of the genetically divergent ancestral populations and the strength of introgression or gene flow. These results demonstrate that even small fractions of introgression or gene flow from ancient populations may have large effects on the inference of effective population size.

scholarly journals O equilíbrio de Hardy-Weinberg no sistema sanguíneo ABO: um estudo de caso em Engenheiro Coelho – SP

2021 ◽  
Vol 43 ◽  
pp. e16
Author(s):  
Vinícius Freitas de Oliveira ◽  
Guilherme Augusto Pianezzer ◽  
Suzete Maria Silva Afonso
Keyword(s):  
Random Mating ◽  
Natural Populations ◽  
Human Populations ◽  
Gene Frequencies ◽  
Weinberg Equilibrium ◽  
Blood Types ◽  
Infinite Population ◽  
Hardy Weinberg Equilibrium ◽  
And Migration

The genetics of human populations is the branch of Genetics that studies the dynamics of genes in natural populations, aiming at the elucidation of mechanisms that alter their genetic composition. Among the fundamentals of this science is the Hardy-Weinberg Equilibrium, which determines that gene frequencies remain unchanged and genotypic proportions reach a stable balance, obtaining the same constant relation with each other over time. To demonstrate this principle, it is necessary to admit that the studied population is not subject to evolutionary factors or to those that alter genotypic frequencies, increasing the homozygosity. More specifically, it is necessary to assume that the population obeys the following premises: random mating, infinite population, non-overlapping generations, in addition to the absence of mutation, selection and migration. More than recalling basic concepts of Genetics and Statistics, this article aims to describe the Bernstein Method for verifying the gene equilibrium for blood types. The research is concluded with a case study in the city of Engenheiro Coelho - SP, where the Hardy-Weinberg Equilibrium for blood types in the population is verified.

scholarly journals Ancestral Admixture Is the Main Determinant of Global Biodiversity in Fission Yeast

2019 ◽  
Vol 36 (9) ◽  
pp. 1975-1989 ◽  
Author(s):  
Sergio Tusso ◽  
Bart P S Nieuwenhuis ◽  
Fritz J Sedlazeck ◽  
John W Davey ◽  
Daniel C Jeffares ◽  
...  
Keyword(s):  
Single Molecule ◽  
Phenotypic Variation ◽  
Natural Populations ◽  
Strand Break ◽  
Transgressive Segregation ◽  
Genomic Variation ◽  
Population History ◽  
Structural Genomic ◽  
History Of ◽  
Reproductive Compatibility

Abstract Mutation and recombination are key evolutionary processes governing phenotypic variation and reproductive isolation. We here demonstrate that biodiversity within all globally known strains of Schizosaccharomyces pombe arose through admixture between two divergent ancestral lineages. Initial hybridization was inferred to have occurred ∼20–60 sexual outcrossing generations ago consistent with recent, human-induced migration at the onset of intensified transcontinental trade. Species-wide heritable phenotypic variation was explained near-exclusively by strain-specific arrangements of alternating ancestry components with evidence for transgressive segregation. Reproductive compatibility between strains was likewise predicted by the degree of shared ancestry. To assess the genetic determinants of ancestry block distribution across the genome, we characterized the type, frequency, and position of structural genomic variation using nanopore and single-molecule real-time sequencing. Despite being associated with double-strand break initiation points, over 800 segregating structural variants exerted overall little influence on the introgression landscape or on reproductive compatibility between strains. In contrast, we found strong ancestry disequilibrium consistent with negative epistatic selection shaping genomic ancestry combinations during the course of hybridization. This study provides a detailed, experimentally tractable example that genomes of natural populations are mosaics reflecting different evolutionary histories. Exploiting genome-wide heterogeneity in the history of ancestral recombination and lineage-specific mutations sheds new light on the population history of S. pombe and highlights the importance of hybridization as a creative force in generating biodiversity.

scholarly journals The influence of demography, population structure and selection on molecular diversity in the selfing freshwater snail Biomphalaria pfeifferi

2003 ◽  
Vol 81 (3) ◽  
pp. 193-204 ◽  
Author(s):  
BERNARD ANGERS ◽  
NATHALIE CHARBONNEL ◽  
NICOLAS GALTIER ◽  
PHILIPPE JARNE
Keyword(s):  
Population Structure ◽  
Mitochondrial Gene ◽  
Random Mating ◽  
Natural Populations ◽  
Freshwater Snail ◽  
Biomphalaria Pfeifferi ◽  
African Populations ◽  
Size Population ◽  
History Of

Several forces may affect the distribution of genetic diversity in natural populations when compared to what is expected in a random-mating, constant size population of neutral genes. One solution for unravelling their respective influence is to study several genes at once in order to better reflect the true genealogy. Here we reconstruct the evolutionary history of the freshwater snail Biomphalaria pfeifferi over its entire distribution, using eight African populations, and three congeneric species as outgroups. A phylogenetic analysis was conducted using amplified fragment length polymorphism markers, and sequences at eight nuclear non-coding loci and one mitochondrial gene were used to analyse population structure. The geographic distribution of variation suggests greater affinities within than among regions. The pattern of variability at both the nuclear and mitochondrial DNA (mtDNA) loci is consistent with a bottleneck, although population structure may also partly explain our results. Our results are also indicative of the role of selection, whether positive or purifying, in the mtDNA. This highlights the fact that the interfering influences of population structure, demography and selection on molecular variation are not easily distinguished.

scholarly journals Insights into human genetic variation and population history from 929 diverse genomes

Science ◽  
2020 ◽  
Vol 367 (6484) ◽  
pp. eaay5012 ◽  
Author(s):  
Anders Bergström ◽  
Shane A. McCarthy ◽  
Ruoyun Hui ◽  
Mohamed A. Almarri ◽  
Qasim Ayub ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Central Africa ◽  
Population History ◽  
Human Populations ◽  
Genome Sequences ◽  
High Coverage ◽  
Geographical Regions ◽  
History Of ◽  
Different Populations ◽  
Source Populations

Genome sequences from diverse human groups are needed to understand the structure of genetic variation in our species and the history of, and relationships between, different populations. We present 929 high-coverage genome sequences from 54 diverse human populations, 26 of which are physically phased using linked-read sequencing. Analyses of these genomes reveal an excess of previously undocumented common genetic variation private to southern Africa, central Africa, Oceania, and the Americas, but an absence of such variants fixed between major geographical regions. We also find deep and gradual population separations within Africa, contrasting population size histories between hunter-gatherer and agriculturalist groups in the past 10,000 years, and a contrast between single Neanderthal but multiple Denisovan source populations contributing to present-day human populations.

Individual variation in inbreeding depression: the roles of inbreeding history and mutation.

Genetics ◽  
1995 ◽  
Vol 141 (3) ◽  
pp. 1209-1223 ◽  
Author(s):  
S T Schultz ◽  
J H Willis
Keyword(s):  
Inbreeding Depression ◽  
Individual Variation ◽  
Random Mating ◽  
Rapid Evolution ◽  
Mixed Mating ◽  
Selfing Rate ◽  
Genetic Associations ◽  
Short Period ◽  
Mating Population ◽  
History Of

Abstract We use mutation-selection recursion models to evaluate the relative contributions of mutation and inbreeding history to variation among individuals in inbreeding depression and the ability of experiments to detect associations between individual inbreeding depression and mating system genotypes within populations. Poisson mutation to deleterious additive or recessive alleles generally produces far more variation among individuals in inbreeding depression than variation in history of inbreeding, regardless of selfing rate. Moreover, variation in inbreeding depression can be higher in a completely outcrossing or selfing population than in a mixed-mating population. In an initially random mating population, the spread of a dominant selfing modifier with no pleiotropic effects on male outcross success causes a measurable increase in inbreeding depression variation if its selfing rate is large and inbreeding depression is caused by recessive lethals. This increase is observable during a short period as the modifier spreads rapidly to fixation. If the modifier alters selfing rate only slightly, it fails to spread or causes no measurable increase in inbreeding depression variance. These results suggest that genetic associations between mating loci and inbreeding depression loci could be difficult to demonstrate within populations and observable only transiently during rapid evolution to a substantially new selfing rate.

scholarly journals Ancestral admixture is the main determinant of global biodiversity in fission yeast

2018 ◽  
Author(s):  
Sergio Tusso ◽  
Bart P.S. Nieuwenhuis ◽  
Fritz J. Sedlazeck ◽  
John W. Davey ◽  
Daniel Jeffares ◽  
...  
Keyword(s):  
Single Molecule ◽  
Phenotypic Variation ◽  
Natural Populations ◽  
Strand Break ◽  
Transgressive Segregation ◽  
Genomic Variation ◽  
Population History ◽  
Structural Genomic ◽  
History Of ◽  
Reproductive Compatibility

Mutation and recombination are key evolutionary processes governing phenotypic variation and reproductive isolation. We here demonstrate that biodiversity within all globally known strains of Schizosaccharomyces pombe arose through admixture between two divergent ancestral lineages. Initial hybridization occurred ~20 sexual outcrossing generations ago consistent with recent, human-induced migration at the onset of intensified transcontinental trade. Species-wide heritable phenotypic variation was explained near-exclusively by strain-specific arrangements of alternating ancestry components with evidence for transgressive segregation. Reproductive compatibility between strains was likewise predicted by the degree of shared ancestry. To assess the genetic determinants of ancestry block distribution across the genome, we characterized the type, frequency and position of structural genomic variation (SV) using nanopore and single-molecule real time sequencing, discovering over 800 SVs. Despite being associated with double-strand break initiation points, SV exerted overall little influence on the introgression landscape or on reproductive compatibility that exist between strains. In contrast, we find strongly increased statistical linkage between ancestral populations that is consistent with negative epistatic selection shaping genomic ancestry combinations during the course of hybridization. This study provides a detailed, experimentally tractable example that genomes of natural populations are mosaics reflecting different evolutionary histories. Exploiting genome-wide heterogeneity in the history of ancestral recombination and lineage-specific mutations sheds new light on the population history of S. pombe and highlights the importance of hybridization as a creative force in generating biodiversity.

scholarly journals Assortative mating by population of origin in a mechanistic model of admixture

2019 ◽  
Author(s):  
Amy Goldberg ◽  
Ananya Rastogi ◽  
Noah A Rosenberg
Keyword(s):  
Assortative Mating ◽  
Mechanistic Model ◽  
Random Mating ◽  
Population History ◽  
Source Population ◽  
Mating Preferences ◽  
Positive Assortative Mating ◽  
Special Cases ◽  
Mating Population ◽  
Over Time

AbstractPopulations whose mating pairs have levels of similarity in phenotypes or genotypes that differ systematically from the level expected under random mating are described as experiencing assortative mating. Excess similarity in mating pairs is termed positive assortative mating, and excess dissimilarity is negative assortative mating. In humans, empirical studies suggest that mating pairs from various admixed populations—whose ancestry derives from two or more source populations—possess correlated ancestry components that indicate the occurrence of positive assortative mating on the basis of ancestry. Generalizing a two-sex mechanistic admixture model, we devise a model of one form of ancestry-assortative mating that occurs through preferential mating based on source population. Under the model, we study the moments of the admixture fraction distribution for different assumptions about mating preferences, including both positive and negative assortative mating by population. We consider the special cases of assortative mating by population that involve a single admixture event and that consider a model of constant contributions to the admixed population over time. We demonstrate that whereas the mean admixture under assortative mating is equivalent to that of a corresponding randomly mating population, the variance of admixture depends on the level and direction of assortative mating. In contrast to standard settings in which positive assortment increases variation within a population, certain assortative mating scenarios allow the variance of admixture to decrease relative to a corresponding randomly mating population: with the three populations we consider, the variance-increasing effect of positive assortative mating within a population might be overwhelmed by a variance-decreasing effect emerging from mating preferences involving other pairs of populations. The effect of assortative mating is smaller on the X chromosome than the autosomes because inheritance of the X in males depends only on the mother’s ancestry, not on the mating pair. Because the variance of admixture is informative about the timing of admixture and possibly about sex-biased admixture contributions, the effects of assortative mating are important to consider in inferring features of population history from distributions of admixture values. Our model provides a framework to quantitatively study assortative mating under flexible scenarios of admixture over time.

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