scholarly journals Genetic load has potential in large populations but is realized in small inbred populations

2021 ◽  
Author(s):  
Samarth Mathur ◽  
J. Andrew DeWoody
Keyword(s):  
Genetic Load ◽  
Large Populations ◽  
Inbred Populations

scholarly journals Temporally balanced selection during development of larval Pacific oysters ( Crassostrea gigas ) inherently preserves genetic diversity within offspring

2021 ◽  
Vol 288 (1958) ◽  
pp. 20203223
Author(s):  
Evan Durland ◽  
Pierre De Wit ◽  
Chris Langdon
Keyword(s):  
Genetic Diversity ◽  
Crassostrea Gigas ◽  
Life Histories ◽  
Developmental Stages ◽  
Balancing Selection ◽  
Genetic Load ◽  
Selection Pressures ◽  
Pacific Oysters ◽  
The Pacific ◽  
Large Populations

Balancing selection is one of the mechanisms which has been proposed to explain the maintenance of genetic diversity in species across generations. For species with large populations and complex life histories, however, heterogeneous selection pressures may create a scenario in which the net effects of selection are balanced across developmental stages. With replicated cultures and a pooled sequencing approach, we show that genotype-dependent mortality in larvae of the Pacific oyster ( Crassostrea gigas ) is largely temporally dynamic and inconsistently in favour of a single genotype or allelic variant at each locus. Overall, the patterns of genetic change we observe to be taking place are more complex than what would be expected under classical examples of additive or dominant genetic interactions. They are also not easily explained by our current understanding of the effects of genetic load. Collectively, temporally heterogeneous selection pressures across different larval developmental stages may act to maintain genetic diversity, while also inherently sheltering genetic load within oyster populations.

scholarly journals An evolutionary perspective on contemporary genetic load in threatened species to inform future conservation efforts

2021 ◽  
Author(s):  
Samarth Mathur ◽  
John Tomeček ◽  
Luis Tarango-Arámbula ◽  
Robert Perez ◽  
Andrew DeWoody
Keyword(s):  
Population Genomics ◽  
Empirical Distribution ◽  
Demographic History ◽  
Genetic Load ◽  
Purifying Selection ◽  
Deleterious Mutations ◽  
Genetic Rescue ◽  
Isolated Populations ◽  
Potential Donor ◽  
Inbred Populations

In theory, genomic erosion can be reduced in fragile “recipient” populations by translocating individuals from genetically diverse “donor” populations. However, recent simulation studies have argued that such translocations can, in principle, serve as a conduit for new deleterious mutations to enter recipient populations. A reduction in evolutionary fitness is associated with a higher load of deleterious mutations and thus, a better understanding of evolutionary processes driving the empirical distribution of deleterious mutations is crucial. Here, we show that genetic load is evolutionarily dynamic in nature and that demographic history greatly influences the distribution of deleterious mutations over time. Our analyses, based on both demographically explicit simulations as well as whole genome sequences of potential donor-recipient pairs of Montezuma Quail (Cyrtonyx montezumae) populations, indicate that all populations tend to lose deleterious mutations during bottlenecks, but that genetic purging is pronounced in smaller populations with stronger bottlenecks. Despite carrying relatively fewer deleterious mutations, we demonstrate how small, isolated populations are more likely to suffer inbreeding depression as deleterious mutations that escape purging are homogenized due to drift, inbreeding, and ineffective purifying selection. We apply a population genomics framework to showcase how the phylogeography and historical demography of a given species can enlighten genetic rescue efforts. Our data suggest that small, inbred populations should benefit the most when assisted gene flow stems from genetically diverse donor populations that have the lowest proportion of deleterious mutations.

scholarly journals Discovery of runs-of-homozygosity diplotype clusters and their associations with diseases in UK Biobank

2020 ◽  
Author(s):  
Ardalan Naseri ◽  
Degui Zhi ◽  
Shaojie Zhang
Keyword(s):  
Demographic History ◽  
Hfe Gene ◽  
Uk Biobank ◽  
Runs Of Homozygosity ◽  
Genome Wide ◽  
A Genome ◽  
Large Populations ◽  
History Of ◽  
Outbred Populations ◽  
Inbred Populations

AbstractRuns of homozygosity (ROH) segments, contiguous homozygous regions in a genome were traditionally linked to families and inbred populations. However, a growing literature suggests that ROHs are ubiquitous in outbred populations. Still, most existing genetic studies of ROH in populations are limited to aggregated ROH content across the genome, which does not offer the resolution for mapping causal loci. This limitation is mainly due to a lack of methods for efficient identification of shared ROH diplotypes. Here, we present a new method, ROH-DICE, to find large ROH diplotype clusters, sufficiently long ROHs shared by a sufficient number of individuals, in large cohorts. ROH-DICE identified over 1 million ROH diplotypes that span over 100 SNPs and shared by more than 100 UK Biobank participants. Moreover, we found significant associations of clustered ROH diplotypes across the genome with various self-reported diseases, with the strongest associations found between the extended HLA region and autoimmune disorders. We found an association between a diplotype covering the HFE gene and haemochromatosis, even though the well-known causal SNP was not directly genotyped nor imputed. Using genome-wide scan, we identified a putative association between carriers of an ROH diplotype in chromosome 4 and an increase of mortality among COVID-19 patients. In summary, our ROH-DICE method, by calling out large ROH diplotypes in a large outbred population, enables further population genetics into the demographic history of large populations. More importantly, our method enables a new genome-wide mapping approach for finding disease-causing loci with multi-marker recessive effects at population scale.

scholarly journals Extreme distribution of deleterious variation in a historically small and isolated population - insights from the Greenlandic Inuit

2016 ◽  
Author(s):  
Casper-Emil T. Pedersen ◽  
Kirk E. Lohmueller ◽  
Niels Grarup ◽  
Peter Bjerregaard ◽  
Torben Hansen ◽  
...  
Keyword(s):  
Genetic Model ◽  
Genetic Load ◽  
Recessive Model ◽  
Deleterious Alleles ◽  
African Populations ◽  
Large Populations ◽  
Population Sizes ◽  
Extreme Distribution ◽  
Inuit Population ◽  
Recent Bottleneck

AbstractThe genetic consequences of a severe bottleneck on genetic load in humans are widely disputed. Based on exome sequencing of 18 Greenlandic Inuit we show that the Inuit have undergone a severe ~20,000 yearlong bottleneck. This has led to a markedly more extreme distribution of deleterious alleles than seen for any other human population. Compared to populations with much larger population sizes, we see an overall reduction in the number of variable sites, increased numbers of fixed sites, a lower heterozygosity, and increased mean allele frequency as well as more homozygous deleterious genotypes. This means, that the Inuit population is the perfect population to examine the effect of a bottleneck on genetic load. Compared to the European, Asian and African populations, we do not observe a difference in the overall number of derived alleles. In contrast, using proxies for genetic load we find that selection has acted less efficiently in the Inuit, under a recessive model. This fits with our simulations that predict a similar number of derived alleles but a true higher genetic load for the Inuit regardless of the genetic model. Finally, we find that the Inuit population has a great potential for mapping of disease-causing variants that are rare in large populations. In fact, we show that these alleles are more likely to be common, and thus easy to map, in the Inuit than in the Finnish and Latino populations; populations considered highly valuable for mapping studies due to recent bottleneck events.

scholarly journals Older fathers' children have lower evolutionary fitness across four centuries and in four populations

2016 ◽  
Author(s):  
Ruben C. Arslan ◽  
Kai P. Willführ ◽  
Emma Frans ◽  
Karin J. H. Verweij ◽  
Mikko Myrskylä ◽  
...  
Keyword(s):  
De Novo ◽  
Child Survival ◽  
Genetic Load ◽  
Age Effects ◽  
Paternal Age ◽  
De Novo Mutations ◽  
Delayed Reproduction ◽  
Large Populations ◽  
Sibling Control ◽  
Control Study

Higher paternal age at offspring conception increases de novo genetic mutations (Kong et al., 2012). Based on evolutionary genetic theory we predicted that the offspring of older fathers would be less likely to survive and reproduce, i.e. have lower fitness. In a sibling control study, we find clear support for negative paternal age effects on offspring survival, mating and reproductive success across four large populations with an aggregate N > 1.3 million in main analyses. Compared to a sibling born when the father was 10 years younger, individuals had 4-13% fewer surviving children in the four populations. Three populations were pre-industrial (1670-1850) Western populations and showed a pattern of paternal age effects across the offspring's lifespan. In 20th-century Sweden, we found no negative paternal age effects on child survival or marriage odds. Effects survived tests for competing explanations, including maternal age and parental loss. To the extent that we succeeded in isolating a mutation-driven effect of paternal age, our results can be understood to show that de novo mutations reduce offspring fitness across populations and time. We can use this understanding to predict the effect of increasingly delayed reproduction on offspring genetic load, mortality and fertility.

Morphogenetic machines revealed: Microscopy of living cells in the embryo of the frog, Xenopus laevis

1993 ◽  
Vol 51 ◽  
pp. 172-173
Author(s):  
Ray Keller
Keyword(s):  
Image Processing ◽  
Fluorescent Dyes ◽  
Cell Movement ◽  
Living Cells ◽  
Ease Of Use ◽  
Low Light ◽  
Amphibian Embryo ◽  
Large Populations ◽  
Light Fluorescence ◽  
Video Image Processing

The amphibian embryo offers advantages of size, availability, and ease of use with both microsurgical and molecular methods in the analysis of fundamental developmental and cell biological problems. However, conventional wisdom holds that the opacity of this embryo limits the use of methods in optical microscopy to resolve the cell motility underlying the major shape-generating processes in early development.These difficulties have been circumvented by refining and adapting several methods. First, methods of explanting and culturing tissues were developed that expose the deep, nonepithelial cells, as well as the superficial epithelial cells, to the view of the microscope. Second, low angle epi-illumination with video image processing and recording was used to follow patterns of cell movement in large populations of cells. Lastly, cells were labeled with vital, fluorescent dyes, and their behavior recorded, using low-light, fluorescence microscopy and image processing. Using these methods, the details of the cellular protrusive activity that drives the powerful convergence (narrowing)

The Use of Medical Record Linkage for Population and Genetic Studies

1969 ◽  
Vol 08 (01) ◽  
pp. 07-11 ◽  
Author(s):  
H. B. Newcombe
Keyword(s):  
Record Linkage ◽  
Large Scale ◽  
Medical Record Linkage ◽  
Canadian Province ◽  
Genetic Studies ◽  
Parental Characteristics ◽  
Family Histories ◽  
The Family ◽  
Large Populations ◽  
Machine Readable

Methods are described for deriving personal and family histories of birth, marriage, procreation, ill health and death, for large populations, from existing civil registrations of vital events and the routine records of ill health. Computers have been used to group together and »link« the separately derived records pertaining to successive events in the lives of the same individuals and families, rapidly and on a large scale. Most of the records employed are already available as machine readable punchcards and magnetic tapes, for statistical and administrative purposes, and only minor modifications have been made to the manner in which these are produced.As applied to the population of the Canadian province of British Columbia (currently about 2 million people) these methods have already yielded substantial information on the risks of disease: a) in the population, b) in relation to various parental characteristics, and c) as correlated with previous occurrences in the family histories.

Sign in / Sign up

Export Citation Format

Share Document