Deleterious mutations and the evolution of sexual reproduction

Nature ◽  
1988 ◽  
Vol 336 (6198) ◽  
pp. 435-440 ◽  
Author(s):  
Alexey S. Kondrashov
Keyword(s):  
Sexual Reproduction ◽  
Deleterious Mutations

scholarly journals Limited Dispersal, Deleterious Mutations and the Evolution of Sex

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 1053-1060
Author(s):  
Joel R Peck
Keyword(s):  
Mathematical Model ◽  
Sexual Reproduction ◽  
Genetic Locus ◽  
Genetic Material ◽  
Plant Population ◽  
Deleterious Mutations ◽  
Animal Populations ◽  
Offspring Sex ◽  
Limited Dispersal ◽  
Hermaphroditic Plant

Abstract This study presents a mathematical model that allows for some offspring to be dispersed at random, while others stay close to their mothers. A single genetic locus is assumed to control fertility, and this locus is subject to the occurrence of deleterious mutations. It is shown that, at equilibrium, the frequency of deleterious mutations in the population is inversely related to the rate of dispersal. This is because dispersal of offspring leads to enhanced competition among adults. The results also show that sexual reproduction can lead to a decrease in the equilibrium frequency of deleterious mutations. The reason for this relationship is that sex involves the dispersal of genetic material, and thus, like the dispersal of offspring, sex enhances competition among adults. The model is described using the example of a hermaphroditic plant population. However, the results should apply to animal populations as well.

scholarly journals The Advantages of Segregation and the Evolution of Sex

Genetics ◽  
2003 ◽  
Vol 164 (3) ◽  
pp. 1099-1118 ◽  
Author(s):  
Sarah P Otto
Keyword(s):  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Deleterious Mutations ◽  
Evolution Of Sex ◽  
Beneficial Mutations ◽  
Selection Regime ◽  
Strong Selection ◽  
Genome Wide ◽  
Low Levels

AbstractIn diploids, sexual reproduction promotes both the segregation of alleles at the same locus and the recombination of alleles at different loci. This article is the first to investigate the possibility that sex might have evolved and been maintained to promote segregation, using a model that incorporates both a general selection regime and modifier alleles that alter an individual’s allocation to sexual vs. asexual reproduction. The fate of different modifier alleles was found to depend strongly on the strength of selection at fitness loci and on the presence of inbreeding among individuals undergoing sexual reproduction. When selection is weak and mating occurs randomly among sexually produced gametes, reductions in the occurrence of sex are favored, but the genome-wide strength of selection is extremely small. In contrast, when selection is weak and some inbreeding occurs among gametes, increased allocation to sexual reproduction is expected as long as deleterious mutations are partially recessive and/or beneficial mutations are partially dominant. Under strong selection, the conditions under which increased allocation to sex evolves are reversed. Because deleterious mutations are typically considered to be partially recessive and weakly selected and because most populations exhibit some degree of inbreeding, this model predicts that higher frequencies of sex would evolve and be maintained as a consequence of the effects of segregation. Even with low levels of inbreeding, selection is stronger on a modifier that promotes segregation than on a modifier that promotes recombination, suggesting that the benefits of segregation are more likely than the benefits of recombination to have driven the evolution of sexual reproduction in diploids.

scholarly journals Sexual selection and its effect on the fixation of an asexual clone

2006 ◽  
Vol 2 (4) ◽  
pp. 536-538 ◽  
Author(s):  
Marcel Salathé
Keyword(s):  
Sexual Selection ◽  
Sexual Reproduction ◽  
Mutation Rates ◽  
Male Mating ◽  
Mutational Load ◽  
Deleterious Mutations ◽  
Sexual Population ◽  
Fitness Advantage ◽  
Genomic Mutation ◽  
Cost Of Sex

Sexual selection is a powerful and ubiquitous force in sexual populations. It has recently been argued that sexual selection can eliminate the twofold cost of sex even with low genomic mutation rates. By means of differential male mating success, deleterious mutations in males become more deleterious than in females, and it has been shown that sexual selection can drastically reduce the mutational load in a sexual population, with or without any form of epistasis. However, any mechanism that claims to maintain sexual reproduction must be able to prevent the fixation of an asexual mutant clone with a twofold fitness advantage. Here, I show that despite very strong sexual selection, the fixation of an asexual mutant cannot be prevented under reasonable genomic mutation rates. Sexual selection can have a strong effect on the average mutational load in a sexual population, but as it cannot prevent the fixation of an asexual mutant, it is unlikely to play a key role on the maintenance of sexual reproduction.

scholarly journals Segregation of autosomes during spermatogenesis in the peach-potato aphid (Myzus persicae) (Sulzer) (Hemiptera: Aphididae)

2002 ◽  
Vol 79 (2) ◽  
pp. 119-127 ◽  
Author(s):  
DINAH F. HALES ◽  
MATHEW A. SLOANE ◽  
ALEX C. C. WILSON ◽  
PAUL SUNNUCKS
Keyword(s):  
Sexual Reproduction ◽  
Genetic Markers ◽  
X Chromosome ◽  
Myzus Persicae ◽  
Microsatellite Loci ◽  
Male Meiosis ◽  
Deleterious Mutations ◽  
Potato Aphid ◽  
Genetic Imprinting ◽  
Peach Potato Aphid

Most aphids are cyclic parthenogens, so are ideal models in studies of the mechanisms and consequences of sex and recombination. However, owing to a shortage of physical and genetic markers, there have been few studies of the most fundamental genetic processes in these organisms. For example, it is not known whether autosomal segregation during male spermatogenesis is in Mendelian proportions: we address that question here. The aphid Myzus persicae has a typical karyotype of 2n = 12 in females (XX), while males are XO (2n = 11). During male meiosis, only the spermatocytes with an X chromosome are viable. We hypothesized that assortment of autosomes might be non-random because chromosomal imprinting leading to elimination of the paternal autosomes is seen in the closely related coccoids. In other aphid models, we have observed segregation distortions at single microsatellite loci (Wilson, 2000). Such distortions may have nothing to do with ‘selfish’ behaviour, but may be caused by mutation accumulation causing fitness differentials. Thus single-locus distortions might be predicted to be more likely to be detected via the male lines of clones that have lost the ability to reproduce sexually (male-producing obligate parthenogenesis (androcyclic)). Using microsatellites we show that genetic imprinting or selfish autosome behaviour does not occur in male M. persicae. Generally, loci segregated in Mendelian proportions in both sexes of cyclically parthenogenetic (holocyclic) clones. However, in androcyclic clones, segregation distortions consistently involved the same two autosomes. This is consistent with linkage of markers to deleterious mutations associated with a loss of sexual reproduction.

Elimination of altered karyotypes by sexual reproduction preserves species identity

Genome ◽  
2007 ◽  
Vol 50 (5) ◽  
pp. 517-524 ◽  
Author(s):  
Henry H.Q. Heng
Keyword(s):  
Genetic Diversity ◽  
Sexual Reproduction ◽  
Cancer Cells ◽  
Evolutionary Biology ◽  
Genetic Recombination ◽  
Deleterious Mutations ◽  
Species Identity ◽  
Sexual Process ◽  
Controlled Reproduction ◽  
Chromosome Level

Resolving the persistence of sexual reproduction despite its overwhelming costs (known as the paradox of sex) is one of the most persistent challenges of evolutionary biology. In thinking about this paradox, the focus has traditionally been on the evolutionary benefits of genetic recombination in generating offspring diversity and purging deleterious mutations. The similarity of pattern between evolution of organisms and evolution among cancer cells suggests that the asexual process generates more diverse genomes owing to less controlled reproduction systems, while sexual reproduction generates more stable genomes because the sexual process can serve as a mechanism to “filter out” aberrations at the chromosome level. Our reinterpretation of data from the literature strongly supports this hypothesis. Thus, the principal consequence of sexual reproduction is the reduction of drastic genetic diversity at the genome or chromosome level, resulting in the preservation of species identity rather than the provision of evolutionary diversity for future environmental challenges. Genetic recombination does contribute to genetic diversity, but it does so secondarily and within the framework of the chromosomally defined genome.

scholarly journals Fitness Effects of Somatic Mutations Accumulating during Vegetative Growth

2018 ◽  
Author(s):  
Mitchell B. Cruzan ◽  
Matthew A. Streisfeld ◽  
Jaime A. Schwoch
Keyword(s):  
Sexual Reproduction ◽  
Somatic Mutation ◽  
Vegetative Growth ◽  
Somatic Mutations ◽  
Life Form ◽  
Deleterious Mutations ◽  
Mimulus Guttatus ◽  
Next Generation ◽  
Fitness Effects ◽  
Offspring Fitness

AbstractThe unique life form of plants promotes the accumulation of somatic mutations that can be passed to offspring in the next generation, because the same meristem cells responsible for vegetative growth also generate gametes for sexual reproduction. However, little is known about the consequences of somatic mutation accumulation for offspring fitness. We evaluate the fitness effects of somatic mutations in Mimulus guttatus by comparing progeny from self-pollinations made within the same flower (autogamy) to progeny from self-pollinations made between stems on the same plant (geitonogamy). The effects of somatic mutations are evident from this comparison, as autogamy leads to homozygosity of a proportion of somatic mutations, but progeny from geitonogamy remain heterozygous for mutations unique to each stem. In two different experiments, we find consistent fitness effects of somatic mutations from individual stems. Surprisingly, several progeny groups from autogamous crosses displayed increases in fitness compared to progeny from geitonogamy crosses, indicating that beneficial somatic mutations were prevalent in some stems. These results support the hypothesis that somatic mutations accumulate during vegetative growth, but they are filtered by different forms of selection that occur throughout development, resulting in the culling of expressed deleterious mutations and the retention of beneficial mutations.

Life cycle of Spirogyra decimina var. juergensii (Kütz.) O.V. Petlovany from Lake Baikal

2018 ◽  
pp. 1-7
Author(s):  
Ekaterina A. Volkova
Keyword(s):  
Life Cycle ◽  
Sexual Reproduction ◽  
Lake Baikal

Identification of Spirogyra species is based on the morphology of the fertile specimens. This work provides characteristics of growth and the time of reproduction of Spirogyra decimina var. juergensii in Lake Baikal and describes sexual reproduction and conditions for germination of new filaments of this species isolated from the lake.

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