scholarly journals Mutation load decreases with haplotype age in wild Soay sheep

2021 ◽  
Author(s):  
Martin A. Stoffel ◽  
Susan E. Johnston ◽  
Jill G. Pilkington ◽  
Josephine M. Pemberton
Keyword(s):  
Mutation Load ◽  
Soay Sheep

scholarly journals Mutation load decreases with haplotype age in wild Soay sheep

2021 ◽  
Author(s):  
M.A. Stoffel ◽  
S.E. Johnston ◽  
J.G. Pilkington ◽  
J.M Pemberton
Keyword(s):  
Inbreeding Depression ◽  
Purifying Selection ◽  
Small Population ◽  
First Year ◽  
Mutation Load ◽  
Soay Sheep ◽  
Recessive Mutations ◽  
Deleterious Alleles ◽  
Lower Population

AbstractRuns of homozygosity (ROH) are pervasive in diploid genomes and expose the effects of deleterious recessive mutations, but how exactly these regions contribute to variation in fitness remains unclear. Here, we combined empirical analyses and simulations to explore the deleterious effects of ROH with varying genetic map lengths in wild Soay sheep. Using a long-term dataset of 4,592 individuals genotyped at 417K SNPs, we found that inbreeding depression increases with ROH length. A 1% genomic increase in long ROH (>12.5cM) reduced the odds of first-year survival by 12%, compared to only 7% for medium ROH (1.56-12.5cM), while short ROH (<1.56cM) had no effect on survival. We show by forward genetic simulations that this is predicted: compared with shorter ROH, long ROH will have higher densities of deleterious alleles, with larger average effects on fitness and lower population frequencies. Taken together, our results are consistent with the idea that the mutation load decreases in older haplotypes underlying shorter ROH, where purifying selection has had more time to purge deleterious mutations. Finally, our study demonstrates that strong inbreeding depression can persist despite ongoing purging in a historically small population.

scholarly journals Harmful mutation load in the mitochondrial genomes of cattle breeds

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Sankar Subramanian
Keyword(s):  
Population Size ◽  
Artificial Selection ◽  
Deleterious Mutation ◽  
Genetic Diseases ◽  
Mitochondrial Genomes ◽  
Deleterious Mutations ◽  
Founder Population ◽  
Mutation Load ◽  
Effective Population ◽  
Cattle Breeds

Abstract Objective Domestication of wild animals results in a reduction in the effective population size, and this could affect the deleterious mutation load of domesticated breeds. Furthermore, artificial selection will also contribute to the accumulation of deleterious mutations due to the increased rate of inbreeding among these animals. The process of domestication, founder population size, and artificial selection differ between cattle breeds, which could lead to a variation in their deleterious mutation loads. We investigated this using mitochondrial genome data from 364 animals belonging to 18 cattle breeds of the world. Results Our analysis revealed more than a fivefold difference in the deleterious mutation load among cattle breeds. We also observed a negative correlation between the breed age and the proportion of deleterious amino acid-changing polymorphisms. This suggests a proportionally higher deleterious SNPs in young breeds compared to older breeds. Our results highlight the magnitude of difference in the deleterious mutations present in the mitochondrial genomes of various breeds. The results of this study could be useful in predicting the rate of incidence of genetic diseases in different breeds.

scholarly journals Mutation load at a mimicry supergene sheds new light on the evolution of inversion polymorphisms

2021 ◽  
Author(s):  
Paul Jay ◽  
Mathieu Chouteau ◽  
Annabel Whibley ◽  
Héloïse Bastide ◽  
Hugues Parrinello ◽  
...  
Keyword(s):  
Mutation Load

scholarly journals Nature of Deleterious Mutation Load in Drosophila

Genetics ◽  
1996 ◽  
Vol 144 (4) ◽  
pp. 1993-1999 ◽  
Author(s):  
Peter D Keightley
Keyword(s):  
Deleterious Mutation ◽  
Spontaneous Mutation ◽  
Mutation Accumulation ◽  
Mutation Rates ◽  
Mutation Load ◽  
Spontaneous Mutation Rate ◽  
A Minor ◽  
Chromosome I ◽  
Balancer Chromosomes ◽  
Balancer Chromosome

Much population genetics and evolution theory depends on knowledge of genomic mutation rates and distributions of mutation effects for fitness, but most information comes from a few mutation accumulation experiments in Drosophila in which replicated chromosomes are sheltered from natural selection by a balancer chromosome. I show here that data from these experiments imply the existence of a large class of minor viability mutations with approximately equivalent effects. However, analysis of the distribution of viabilities of chromosomes exposed to EMS mutagenesis reveals a qualitatively different distribution of effects lacking such a minor effects class. A possible explanation for this difference is that transposable element insertions, a common class of spontaneous mutation event in Drosophila, frequently generate minor viability effects. This explanation would imply that current estimates of deleterious mutation rates are not generally applicable in evolutionary models, as transposition rates vary widely. Alternatively, much of the apparent decline in viability under spontaneous mutation accumulation could have been nonmutational, perhaps due to selective improvement of balancer chromosomes. This explanation accords well with the data and implies a spontaneous mutation rate for viability two orders of magnitude lower than previously assumed, with most mutation load attributable to major effects.

scholarly journals The mutation load under tetrasomic inheritance and its consequences for the evolution of the selfing rate in autotetraploid species

1999 ◽  
Vol 74 (1) ◽  
pp. 31-42 ◽  
Author(s):  
J. RONFORT
Keyword(s):  
Inbreeding Depression ◽  
Deleterious Mutation ◽  
Stable State ◽  
Approximate Solutions ◽  
Balance Model ◽  
Deleterious Mutations ◽  
Selfing Rate ◽  
Mutation Load ◽  
Mean Fitness ◽  
The Mean

Single-locus equilibrium frequencies of a partially recessive deleterious mutation under the mutation–selection balance model are derived for partially selfing autotetraploid populations. Assuming multiplicative fitness interactions among loci, approximate solutions for the mean fitness and inbreeding depression values are also derived for the multiple locus case and compared with expectations for the diploid model. As in diploids, purging of deleterious mutations through consanguineous matings occurs in autotetraploid populations, i.e. the equilibrium mutation load is a decreasing function of the selfing rate. However, the variation of inbreeding depression with the selfing rate depends strongly on the dominance coefficients associated with the three heterozygous genotypes. Inbreeding depression can either increase or decrease with the selfing rate, and does not always vary monotonically. Expected issues for the evolution of the selfing rate consequently differ depending on the dominance coefficients. In some cases, expectations for the evolution of the selfing rate resemble expectations in diploids; but particular sets of dominance coefficients can be found that lead to either complete selfing or intermediate selfing rates as unique evolutionary stable state.

scholarly journals The Impact of Environmental and Endogenous Damage on Somatic Mutation Load in Human Skin Fibroblasts

PLoS Genetics ◽  
2016 ◽  
Vol 12 (10) ◽  
pp. e1006385 ◽  
Author(s):  
Natalie Saini ◽  
Steven A. Roberts ◽  
Leszek J. Klimczak ◽  
Kin Chan ◽  
Sara A. Grimm ◽  
...  
Keyword(s):  
Human Skin ◽  
Somatic Mutation ◽  
Skin Fibroblasts ◽  
Human Skin Fibroblasts ◽  
Mutation Load ◽  
The Impact

scholarly journals Gastrointestinal nematode species diversity in Soay sheep kept in a natural environment without active parasite control

2016 ◽  
Vol 227 ◽  
pp. 1-7 ◽  
Author(s):  
Rona Sinclair ◽  
Lynsey Melville ◽  
Fiona Sargison ◽  
Fiona Kenyon ◽  
Dan Nussey ◽  
...  
Keyword(s):  
Species Diversity ◽  
Natural Environment ◽  
Gastrointestinal Nematode ◽  
Nematode Species ◽  
Parasite Control ◽  
Soay Sheep

scholarly journals MUTATION LOAD AND THE SURVIVAL OF SMALL POPULATIONS

Evolution ◽  
1990 ◽  
Vol 44 (7) ◽  
pp. 1725-1737 ◽  
Author(s):  
Michael Lynch ◽  
Wilfried Gabriel
Keyword(s):  
Small Populations ◽  
Mutation Load

scholarly journals Selection, Load and Inbreeding Depression in a Large Metapopulation

Genetics ◽  
2002 ◽  
Vol 160 (3) ◽  
pp. 1191-1202 ◽  
Author(s):  
Michael C Whitlock
Keyword(s):  
Population Structure ◽  
Inbreeding Depression ◽  
Population Subdivision ◽  
Response To Selection ◽  
Mutation Load ◽  
Deleterious Alleles ◽  
Subdivided Population ◽  
Soft Selection ◽  
Mean Fitness ◽  
The Mean

Abstract The subdivision of a species into local populations causes its response to selection to change, even if selection is uniform across space. Population structure increases the frequency of homozygotes and therefore makes selection on homozygous effects more effective. However, population subdivision can increase the probability of competition among relatives, which may reduce the efficacy of selection. As a result, the response to selection can be either increased or decreased in a subdivided population relative to an undivided one, depending on the dominance coefficient FST and whether selection is hard or soft. Realistic levels of population structure tend to reduce the mean frequency of deleterious alleles. The mutation load tends to be decreased in a subdivided population for recessive alleles, as does the expected inbreeding depression. The magnitude of the effects of population subdivision tends to be greatest in species with hard selection rather than soft selection. Population structure can play an important role in determining the mean fitness of populations at equilibrium between mutation and selection.

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