Topic
Mutational meltdown
About: Mutational meltdown is a research topic. Over the lifetime, 140 publications have been published within this topic receiving 13740 citations.
Papers published on a yearly basis
Papers
TL;DR: It is shown that this calculation does not apply for mutant genes that act advantageously only when in some special combinations with one or more other mutant genes, and that as far as these cases of special synergism are concerned recombining lines have no evolutionary advantage over non-recombining ones.
Abstract: The method of calculation is shown wherebt a formula has been derived that approximately the ratio of the rate of accumulation of advantageous mutant genes in a population that undergoes recombination to the rate in an otherwise non-recombining one. A table is given showing the ratios thus found for different frequencies of advantageous mutations and different degrees of their advantage. It is shown that this calculation does not apply for mutant genes that act advantageously only when in some special combinations with one or more other mutant genes, and that as far as these cases of special synergism are concerned recombining lines have no evolutionary advantage over non-recombining ones. Other limitations of the formula are pointed out and assessed. It is explained that most factors that retard the rate of recombination—for expample, linkage, rarity of outbreeding, intercalation of sexual reproduction between more frequent cycles of sexual propagation, and partial isolation between subpopulations—must usually cause little long-term retardation of the speed of advance that is fostered by recombination. Moreover, even where long-term evolutions has virtually ceased, recombination of mutant genes still confers upon a population the means of adopting short-term genetic “dodges”, that adjust it to ecological and “physical” changes in its circumstances, much more rapidly than would be possible for a comparable asexual population. Under conditions where only stability of type is needed, a non-recombining does not actually degenerate as a result of an excess of mutation over selection, after the usual equilibrium between these pressures is reached. However, a irreversible ratchet mechanism exists in the non-recombining species (unlike the recombining ones) that prevents selection, even if intensified, from reducing the mutational loads below the lightest that were in existence when the intensified selection started, whereas, contrariwise, “drift”, and what might be called “selective noise” must allow occasional slips of the lightest loads in the direction of increased weight.
2,518 citations
TL;DR: If the deleterious mutation rate per genome per generation is greater than 1, then the greater efficiency of selection against these mutations in sexual populations may be responsible for the evolution of sex and related phenomena.
Abstract: The origin and maintenance of sexual reproduction continues to be an important problem in evolutionary biology. If the deleterious mutation rate per genome per generation is greater than 1, then the greater efficiency of selection against these mutations in sexual populations may be responsible for the evolution of sex and related phenomena. In modern human populations detrimental mutations with small individual effects are probably accumulating faster than they are being eliminated by selection.
1,168 citations
TL;DR: Application of empirical estimates of the properties of spontaneous deleterious mutations leads to the conclusion that populations with effective sizes smaller than 100 are highly vulnerable to extinction via a mutational meltdown on timescales of approximately 100 generations.
Abstract: Although extensive work has been done on the relationship between population size and the risk of extinction due to demographic and environmental stochasticity, the role of genetic deterioration in the extinction process is poorly understood. We develop a general theoretical approach for evaluating the risk of small populations to extinction via the accumulation of mildly deleterious mutations, and we support this with extensive computer simulations. Unlike previous attempts to model the genetic consequences of small population size, our approach is genetically explicit and fully accounts for the mutations inherited by a founder population as well as those introduced by subsequent mutation. Application of empirical estimates of the properties of spontaneous deleterious mutations leads to the conclusion that populations with effective sizes smaller than 100 (and actual sizes smaller than 1,000) are highly vulnerable to extinction via a mutational meltdown on timescales of approximately 100 generations. We ...
1,052 citations
TL;DR: In a species in equilibrium variation, some deleterious genes are being weeded out by selection at the same rate as they are produced by mutation and the loss of fitness in the species is roughly equal to the sum of all mutation rates.
Abstract: In a species in equilibrium variation is mainly due to two causes. Some deleterious genes are being weeded out by selection at the same rate as they are produced by mutation. Others are preserved because the heterozygous form is fitter than either homozygote. In the former case the loss of fitness in the species is roughly equal to the sum of all mutation rates and is probably of the order of 5 per cent. It is suggested that this loss of fitness is the price paid by a species for its capacity for further evolution.
667 citations
TL;DR: It is shown that the mean extinction time declines as mutations become more deleterious, and although very small sexual populations, such as self‐fertilized lines, are subject to mutational meltdowns, recombination effectively eliminates the process when the effective population size exceeds a dozen or so.
Abstract: Previous attempts to model the joint action of selection and mutation in finite popu- lations have treated population size as being independent of the mutation load. However, the accumulation of deleterious mutations is expected to cause a gradual reduction in population size. Consequently, in small populations random genetic drift will progressively overpower selection making it easier to fix future mutations. This synergistic interaction, which we refer to as a mu- tational melt-down, ultimately leads to population extinction. For many conditions, the coefficient of variation of extinction time is less than 0.1, and for species that reproduce by binary fission, the expected extinction time is quite insensitive to population carrying capacity. These results are consistent with observations that many cultures of ciliated protozoans and vertebrate fibroblasts have characteristic extinction times. The model also predicts that clonal lineages are unlikely to survive more than 104 to 105 generations, which is consistent with existing data on parthenogenetic animals. Contrary to the usual view that Muller's ratchet does more damage when selection is weak, we show that the mean extinction time declines as mutations become more deleterious. Although very small sexual populations, such as self-fertilized lines, are subject to mutational melt- downs, recombination effectively eliminates the process when the effective population size exceeds a dozen or so. The concept of the effective mutation load is developed, and several procedures for estimating it are described. It is shown that this load can be reduced substantially when mutational effects are highly variable.
517 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 2 |
| 2020 | 7 |
| 2019 | 6 |
| 2018 | 5 |
| 2017 | 10 |
| 2016 | 7 |