scholarly journals The Highly Cooperative Folding of Small Naturally Occurring Proteins Is Likely the Result of Natural Selection

Cell ◽  
2007 ◽  
Vol 128 (3) ◽  
pp. 613-624 ◽  
Author(s):  
Alexander L. Watters ◽  
Pritilekha Deka ◽  
Colin Corrent ◽  
David Callender ◽  
Gabriele Varani ◽  
...  
Keyword(s):  
Natural Selection ◽  
Naturally Occurring

scholarly journals Lack of underdominance in a naturally occurring pericentric inversion in Drosophila melanogaster and its implications for chromosome evolution.

Genetics ◽  
1991 ◽  
Vol 129 (3) ◽  
pp. 791-802
Author(s):  
J A Coyne ◽  
S Aulard ◽  
A Berry
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Genetic Drift ◽  
Related Species ◽  
Pericentric Inversion ◽  
Chromosome Evolution ◽  
Natural Populations ◽  
Crossing Over ◽  
Closely Related Species ◽  
Naturally Occurring

Abstract In(2LR)PL is a large pericentric inversion polymorphic in populations of Drosophila melanogaster on two Indian Ocean islands. This polymorphism is puzzling: because crossing over in female heterokaryotypes produces inviable zygotes, such inversions are thought to be underdominant and should be quickly eliminated from populations. The observed fixation for such inversions among related species has led to the idea that genetic drift can cause chromosome evolution in opposition to natural selection. We found, however, that In(2LR)PL is not underdominant for fertility, as heterokaryotypic females produce perfectly viable eggs. Genetic analysis shows that the lack of underdominance results from the nearly complete absence of crossing over in the inverted region. This phenomenon is probably caused by mechanical and not genetic factors, because crossing over is not suppressed in In(2LR)PL homokaryotypes. Our observations do not support the idea that the fixation of pericentric inversions among closely related species implies the action of genetic drift overcoming strong natural selection in very small populations. If chromosome arrangements vary in their underdominance, it is those with the least disadvantage as heterozygotes, like In(2LR)PL, that will be polymorphic or fixed in natural populations.

scholarly journals An Experimental Demonstration of Fisher's Principle: Evolution of Sexual Proportion by Natural Selection

Genetics ◽  
1998 ◽  
Vol 148 (2) ◽  
pp. 719-731
Author(s):  
Antonio Bernardo Carvalho ◽  
Michelle Cristina Sampaio ◽  
Flavia Roque Varandas ◽  
Louis Bernard Klaczko
Keyword(s):  
Natural Selection ◽  
Genetic Variability ◽  
Sex Ratio ◽  
Reproductive Effort ◽  
Meiotic Drive ◽  
Experimental Demonstration ◽  
Biological Phenomenon ◽  
Naturally Occurring ◽  
Experimental Populations ◽  
Fisher’S Principle

Abstract Most sexually reproducing species have sexual proportions around 1:1. This major biological phenomenon remained unexplained until 1930, when Fisher proposed that it results from a mechanism of natural selection. Here we report the first experimental test of his model that obeys all its assumptions. We used a naturally occurring X-Y meiotic drive system—the sex-ratio trait of Drosophila mediopunctata—to generate female-biased experimental populations. As predicted by Fisher, these populations evolved toward equal sex proportions due to natural selection, by accumulation of autosomal alleles that direct the parental reproductive effort toward the rare sex. Classical Fisherian evolution is a rather slow mechanism: despite a very large amount of genetic variability, the experimental populations evolved from 16% of males to 32% of males in 49 generations and would take 330 generations (29 years) to reach 49%. This slowness has important implications for species potentially endangered by skewed sexual proportions, such as reptiles with temperature sex determination.

The adaptive function of sexual reproduction: resampling the pool of genotypic possibilities.

2021 ◽  
Author(s):  
Donal Hickey ◽  
Brian Golding
Keyword(s):  
Genetic Variation ◽  
Natural Selection ◽  
Sexual Reproduction ◽  
Finite Population ◽  
Adaptive Function ◽  
Asexual Population ◽  
Sexual Population ◽  
Naturally Occurring ◽  
The Cost ◽  
The Universe

Abstract BackgroundNatural populations harbor significant levels of genetic variability. Because of this standing genetic variation, the number of possible genotypic combinations is many orders of magnitude greater than the population size. This means that any given population contains only a tiny fraction of all possible genotypic combinations.ResultsWe show that recombination allows a finite population to resample the genotype pool, i.e., the universe of all possible genotypic combinations. Recombination, in combination with natural selection, enables an evolving sexual population to replace existing genotypes with new, higher-fitness genotypic combinations that did not previously exist in the population. Gradually the selected sexual population approaches a state where the optimum genotype is produced by recombination and where it rises to fixation. In contrast to this, an asexual population is limited to selection among existing lower fitness genotypes.ConclusionsThe significance of the result is two-fold. First, it provides an explanation for the ubiquity of sexual reproduction in evolving populations. Secondly, it shows that recombination serves to remove concerns about the cost of natural selection acting on the naturally occurring standing genetic variation. This means that classic population genetics theory is applicable to ecological studies of natural selection acting on standing genetic variation.

Identification of subterranean clover cultivars and their genetic relationships by isozyme analysis

1984 ◽  
Vol 35 (3) ◽  
pp. 399 ◽  
Author(s):  
WJ Collins ◽  
RC Rossiter ◽  
Y Haynes ◽  
AHD Brown ◽  
DR Marshall
Keyword(s):  
Natural Selection ◽  
Genetic Distance ◽  
Genetic Relationships ◽  
Subterranean Clover ◽  
Isozyme Analysis ◽  
Isozyme Patterns ◽  
Naturally Occurring ◽  
Natural Isolates ◽  
Isozyme Loci ◽  
Esterase Patterns

Isozyme patterns for the 22 registered cultivars of Trifolium subterraneurn L. are described for 15 enzymes. The patterns discriminated among all cultivars except that Uniwager was isozymically identical with Geraldton, from which it was derived by deliberate mutation. The 17 cultivars which originally came from naturally occurring isolates, as well as Uniwager, appeared to be isozymically homogeneous, whereas three of the five bred cultivars (Nungarin, Esperance and Howard) were polymorphic for at least one locus. The cultivars indicated that T. subterraneum is highly polymorphic at isozyme loci. Excluding the complex esterase patterns, the species was polymorphic at 21 of 26 putative loci, with an average of 2.3 alleles detected per locus. Estimates of genetic distance between the cultivars stemming from natural isolates strongly supported the classification into three subspecies. In addition, the cultivar Woogenellup (syn Marrar) was well separated from all other cultivars of the subspecies subterraneum. Isozyme surveys should therefore provide critical evidence on the role such factors as introduction, natural selection, mutation and outcrossing have had in the origin of variation within subterranean clover in Australia.

scholarly journals Algorithmically probable mutations reproduce aspects of evolution, such as convergence rate, genetic memory and modularity

2018 ◽  
Vol 5 (8) ◽  
pp. 180399 ◽  
Author(s):  
Santiago Hernández-Orozco ◽  
Narsis A. Kiani ◽  
Hector Zenil
Keyword(s):  
Genetic Algorithms ◽  
Natural Selection ◽  
Convergence Rates ◽  
Biological Evolution ◽  
Natural Approach ◽  
Naturally Occurring ◽  
Binary Matrices ◽  
Accelerate Convergence ◽  
Primitive Forms ◽  
Formal Version

Natural selection explains how life has evolved over millions of years from more primitive forms. The speed at which this happens, however, has sometimes defied formal explanations when based on random (uniformly distributed) mutations. Here, we investigate the application of a simplicity bias based on a natural but algorithmic distribution of mutations (no recombination) in various examples, particularly binary matrices, in order to compare evolutionary convergence rates. Results both on synthetic and on small biological examples indicate an accelerated rate when mutations are not statistically uniform but algorithmically uniform . We show that algorithmic distributions can evolve modularity and genetic memory by preservation of structures when they first occur sometimes leading to an accelerated production of diversity but also to population extinctions, possibly explaining naturally occurring phenomena such as diversity explosions (e.g. the Cambrian) and massive extinctions (e.g. the End Triassic) whose causes are currently a cause for debate. The natural approach introduced here appears to be a better approximation to biological evolution than models based exclusively upon random uniform mutations, and it also approaches a formal version of open-ended evolution based on previous formal results. These results validate some suggestions in the direction that computation may be an equally important driver of evolution. We also show that inducing the method on problems of optimization, such as genetic algorithms, has the potential to accelerate convergence of artificial evolutionary algorithms.

scholarly journals ALLELIC VARIATION AT THE LEVEL OF INTRAGENIC RECOMBINATION

Genetics ◽  
1978 ◽  
Vol 89 (1) ◽  
pp. 211-224
Author(s):  
Michael Freeling
Keyword(s):  
Population Genetics ◽  
Linkage Disequilibrium ◽  
Natural Selection ◽  
Alcohol Dehydrogenase ◽  
Allelic Variation ◽  
Pollen Grains ◽  
Intragenic Recombination ◽  
Naturally Occurring ◽  
Using Data ◽  
Alcohol Dehydrogenase 1

ABSTRACT This report examines five different naturally occurring alcohol dehydrogenase-1 alleles via the recombinational behavior of Adh1  - mutants induced within them. Twenty-two biochemically characterized Adh1  - mutants have been assessed for ability to recombine intragenically, using data generated by specifically staining for the presence of ADH in pollen grains. Each of the five naturally occurring Adh1 progenitor isoalleles appears unique. Allelic variation exists in (1) the rate of intragenic recombination sustained by an allele, and (2) the pattern of recombinational success or failure based on the ancestry of each mutant in a heteroallelic pair. In other words, we find quantitative and qualitative Adh1 allelic variation at the level of intragenic recombination. I have experimentally excluded several explanations for recombinational restriction. These results will be related to the structure, function and naturally occurring variability of the gene in higher organisms. Specifically, the "recon" (unit of recombination) has been resurrected as a potentially useful unit of natural selection. The reasonableness of several genres of hypotheses in evolutionary/population genetics, particularly those involving linkage disequilibrium, is called into question.

Using genetic markers to investigate natural selection in fungal populations

1995 ◽  
Vol 73 (S1) ◽  
pp. 302-310 ◽  
Author(s):  
R. A. Ennos ◽  
K. C. McConnell
Keyword(s):  
Natural Selection ◽  
Genetic Differentiation ◽  
Genetic Markers ◽  
Reciprocal Transplant ◽  
Transplant Experiment ◽  
Reciprocal Transplant Experiment ◽  
Naturally Occurring ◽  
Canker Pathogen ◽  
Fungal Populations ◽  
Response To Environmental Change

Naturally occurring genetic markers can be exploited in a number of ways to measure natural selection in fungal populations. The potentials and pitfalls of these approaches are outlined. A review of existing experiments that have used genetic markers to estimate selection coefficients (s) in experimental and natural fungal populations indicates that differences in fitness between clones, populations, and subspecies may be substantial (mean s = 0.322), and that significant changes in the intensity and direction of selection may occur when environmental conditions alter. A reciprocal transplant experiment is described in which the relative selective values of three genetically marked populations of the canker pathogen Crumenulopsis sororia were compared under natural conditions. Large differences in selective value were found both among populations and within sites, but there was no evidence that genetic differentiation among populations was adaptive. The potential application of genetic markers for experimentally investigating mechanisms of speciation, adaptive genetic differentiation, and response to environmental change in fungi is discussed. Key words: genetic marker, natural selection, selection coefficient, Crumenulopsis sororia.

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