scholarly journals Natural selection as the process of accumulating genetic information in adaptive evolution

1961 ◽  
Vol 2 (1) ◽  
pp. 127-140 ◽  
Author(s):  
Motoo Kimura
Keyword(s):  
Natural Selection ◽  
Adaptive Evolution ◽  
Genetic Information ◽  
Genetic Load ◽  
Genetic Constitution ◽  
Linear Sequence ◽  
A Value ◽  
Darwinian Fitness ◽  
Image Position ◽  
Rate Of Accumulation

1. In the course of evolution, complicated organisms have descended from much simpler ones. Since the instructions to form an organism are contained in the nucleus of its fertilized egg, this means that the genetic constitution has become correspondingly more complex in evolution. If we express this complexity in terms of its improbability, defining the amount of genetic information as the negative logarithm of its probability of occurrence by chance, we may say that genetic information is increased in the course of progressive evolution, guided by natural selection of random mutations.2. It was demonstrated that the rate of accumulation of genetic information in adaptive evolution is directly proportional to the substitutional load, i.e. the decrease of Darwinian fitness brought about by substituting for one gene its allelic form which is more fitted to a new environment. The rate of accumulation of genetic information is given bywhere Le is the substitutional load measured in ‘Malthusian parameters’.3. Using Le = 0·199, a value obtained from the application of the ‘principle of minimum genetic load’ (cf. Kimura, 1960 b), we getIt was estimated that the total amount of genetic information accumulated since the beginning of the Cambrian epoch (500 million years) may be of the order of 108 bits, if evolution has proceeded at the standard rate.Since the genetic information is transformed into phenotypic information in ontogeny, this figure (108 bits) must represent the amount of information which corresponds to the improved organization of higher animals as compared to their ancestors 500 million years back.4. Problems involved in storage and transformation of genetic information thus acquired were discussed and it was pointed out that the redundancy of information in the form of repetition in linear sequence of nucleotide pairs within a gene may play an important role in the storage of genetic information.

scholarly journals Evolutionary stalling and a limit on the power of natural selection to improve a cellular module

2020 ◽  
Vol 117 (31) ◽  
pp. 18582-18590 ◽  
Author(s):  
Sandeep Venkataram ◽  
Ross Monasky ◽  
Shohreh H. Sikaroodi ◽  
Sergey Kryazhimskiy ◽  
Betul Kacar
Keyword(s):  
Escherichia Coli ◽  
Natural Selection ◽  
Adaptive Evolution ◽  
Genetic Load ◽  
Performance Theory ◽  
Biological Functions ◽  
Beneficial Mutations ◽  
Translation Machinery ◽  
Adaptive Mutations ◽  
Organismal Fitness

Cells consist of molecular modules which perform vital biological functions. Cellular modules are key units of adaptive evolution because organismal fitness depends on their performance. Theory shows that in rapidly evolving populations, such as those of many microbes, adaptation is driven primarily by common beneficial mutations with large effects, while other mutations behave as if they are effectively neutral. As a consequence, if a module can be improved only by rare and/or weak beneficial mutations, its adaptive evolution would stall. However, such evolutionary stalling has not been empirically demonstrated, and it is unclear to what extent stalling may limit the power of natural selection to improve modules. Here we empirically characterize how natural selection improves the translation machinery (TM), an essential cellular module. We experimentally evolved populations ofEscherichia coliwith genetically perturbed TMs for 1,000 generations. Populations with severe TM defects initially adapted via mutations in the TM, but TM adaptation stalled within about 300 generations. We estimate that the genetic load in our populations incurred by residual TM defects ranges from 0.5 to 19%. Finally, we found evidence that both epistasis and the depletion of the pool of beneficial mutations contributed to evolutionary stalling. Our results suggest that cellular modules may not be fully optimized by natural selection despite the availability of adaptive mutations.

scholarly journals Evolutionary Stalling and a Limit on the Power of Natural Selection to Improve a Cellular Module

2019 ◽  
Author(s):  
Sandeep Venkataram ◽  
Ross Monasky ◽  
Shohreh H Sikaroodi ◽  
Sergey Kryazhimskiy ◽  
Betül Kaçar
Keyword(s):  
Escherichia Coli ◽  
Natural Selection ◽  
Adaptive Evolution ◽  
Genetic Load ◽  
Performance Theory ◽  
Biological Functions ◽  
Beneficial Mutations ◽  
Translation Machinery ◽  
Adaptive Mutations ◽  
Organismal Fitness

AbstractCells consist of molecular modules which perform vital biological functions. Cellular modules are key units of adaptive evolution because organismal fitness depends on their performance. Theory shows that in rapidly evolving populations, such as those of many microbes, adaptation is driven primarily by common beneficial mutations with large effects, while other mutations behave as if they are effectively neutral. As a consequence, if a module can be improved only by rare and/or weak beneficial mutations, its adaptive evolution would stall. However, such evolutionary stalling has not been empirically demonstrated, and it is unclear to what extent stalling may limit the power of natural selection to improve modules. Here, we empirically characterize how natural selection improves the translation machinery (TM), an essential cellular module. We experimentally evolved populations of Escherichia coli with genetically perturbed TMs for 1,000 generations. Populations with severe TM defects initially adapted via mutations in the TM, but TM adaptation stalled within about 300 generations. We estimate that the genetic load in our populations incurred by residual TM defects ranges from 0.5 to 19%. Finally, we found evidence that both epistasis and the depletion of the pool of beneficial mutations contributed to evolutionary stalling. Our results suggest that cellular modules may not be fully optimized by natural selection despite the availability of adaptive mutations.

scholarly journals GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 569-589
Author(s):  
Martin L Tracey ◽  
Francisco J Ayala
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Natural Population ◽  
Natural Populations ◽  
Genetic Load ◽  
Structural Genes ◽  
Invertebrate Species ◽  
Average Proportion ◽  
Mean Fitness ◽  
The Mean

ABSTRACT Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

scholarly journals IS NATURAL SELECTION A CHIMERA? REFLECTIONS ON THE ‘SURVIVAL’ OF A PRINCIPLE

2017 ◽  
Vol 14 (3) ◽  
Author(s):  
Gláucia Oliveira da Silva
Keyword(s):  
Biological Sciences ◽  
Natural Selection ◽  
Explanatory Power ◽  
Scientific Field ◽  
Self Determination ◽  
Biological Processes ◽  
Social Anthropology ◽  
Victorian Britain ◽  
A Value ◽  
Great Divide

Abstract My objective is to discuss the persistence of the notion of natural selection in the biological sciences, exploring the fact that: (1) this notion, just like the term culture in anthropology, is historically an inaugural concept in its particular scientific field, and, insofar as both possess a value of heuristic delimitation, both thus came to be considered as explanatory concepts, although today they may be more widely accepted as descriptive in kind; (2) this persistence seems to be equally linked to the fact that the term combines randomness and teleology, but without foregrounding the inherent contradiction; (3) the anthropomorphic metaphors generally used in the description of biological processes, by attributing intentionality to beings lacking in self-determination, presume the existence of a nature defined by processes oriented towards precise ends, endorsing the finalism that, I believe, underlies the idea of natural selection; (4) and, finally, I think that ‘culture’ and ‘natural selection’ correspond to disciplinary labels - for social anthropology and biology respectively - that arose in Victorian Britain, as defined by the Great Divide, but they no longer have explanatory power.

The influence of genetic constitution on migraine drug responses

Cephalalgia ◽  
2015 ◽  
Vol 36 (7) ◽  
pp. 624-639 ◽  
Author(s):  
Anne Francke Christensen ◽  
Ann-Louise Esserlind ◽  
Thomas Werge ◽  
Hreinn Stefánsson ◽  
Kári Stefánsson ◽  
...  
Keyword(s):  
Individualized Medicine ◽  
Treatment Success ◽  
Genetic Load ◽  
Genetic Effect ◽  
Genetic Constitution ◽  
Nucleotide Polymorphisms ◽  
Genetic Score ◽  
Drug Responses ◽  
Association Analyses ◽  
Prophylactic Drugs

Objective Specific acute treatments of migraine are 5HT1B/D receptor agonists; triptans and ergotamine, but only two-thirds of patients respond well without side effects. No migraine-prophylactic drugs are specific to migraine. Prophylactic drugs are selected by time-consuming “trial and error.” Personalized treatment is therefore much needed. The objective of this study was to test the effect of 12 single nucleotide polymorphisms (SNPs) significantly associated with migraine on migraine drug responses. Methods Semi-structured migraine interviews including questions on drug responses, blood samples and genotyping were performed on 1806 unrelated migraine cases recruited from the Danish Headache Center. Association analyses were carried out using logistic regression, assuming an additive model for the genetic effect. The effect on drug responses was tested for a combined genetic score and for each of the 12 SNPs. Significant findings were subsequently tested in an independent replication sample of 392 unrelated Danish migraine cases. Results A single risk variant, rs2651899 in PRDM16, was significantly associated with efficacy of triptans with an odds ratio (OR) of treatment success of 1.3, and a higher combined genetic score was significantly associated with efficacy of triptans with an OR of success of up to 2.6. A number of SNPs showed nominal preferential association with the efficacy of triptans and others with prophylactic drugs. Analyses of triptans and ergotamine complemented each other and gave a stronger signal when analyzed together. The associations between response to triptans and genetic load and rs2651899 were partially confirmed in the independent sample. Conclusion We show for the first time an association between genetic constitution and migraine drug response. This is a first step toward future individualized medicine.

scholarly journals Dynamics of natural selection in two generations (on the example of the population of the Kirovograd region)

2021 ◽  
Vol 29 ◽  
pp. 152-156
Author(s):  
K. K. Kovleva ◽  
N.A. Kozak
Keyword(s):  
Natural Selection ◽  
First Generation ◽  
Second Generation ◽  
Selection Index ◽  
Genetic Load ◽  
Modern Medicine ◽  
Reproductive Age ◽  
Human Populations ◽  
Medical Histories ◽  
Total Selection

Aim. In connection with the success of modern medicine, the pressure of natural selection in various civilized human populations is weakening, which leads to the accumulation of a genetic load. The purpose of this work was to trace the change in the intensity of natural selection among population of the Kirovograd region in two successive generations. Methods. The collection of material was carried out in 2020 and 2021. Anonymous questionnaires were conducted and medical histories of women of post-reproductive age of the Kirovograd region were studied. The first generation included 40 women born in 1937–1959; the second generation consists of 273 women born in 1960–1981. Results. The total selection index was 0.27 in the first generation, and 0.37 in the second generation. The percentage of women who have not had pregnancies increased from the first generation to the second from 2.5 to 3.7, respectively. Conclusions. The index of total selection in the Kirovograd region population for one generation increased by almost one and a half times (from 0.27 to 0.37), as well as the index of differential fertility (from 0.25 to 0.35). Keywords: reproductive characteristics, Kirovograd population, Crow's index, selection, generations.

Genetic load and biological changes to extant humans

2020 ◽  
pp. 1-4
Author(s):  
Arthur Saniotis ◽  
Maciej Henneberg ◽  
Kazhaleh Mohammadi
Keyword(s):  
Natural Selection ◽  
Current Knowledge ◽  
Genetic Load ◽  
Differential Fertility ◽  
Medical Interventions ◽  
Deleterious Alleles ◽  
Gradual Process ◽  
Genetic Complexity ◽  
Sexual Recombination ◽  
Improved Sanitation

Abstract Extant humans are currently increasing their genetic load, which is informing present and future human microevolution. This has been a gradual process that has been rising over the last centuries as a consequence of improved sanitation, nutritional improvements, advancements in microbiology and medical interventions, which have relaxed natural selection. Moreover, a reduction in infant and child mortality and changing societal attitudes towards fertility have led to a decrease in total fertility rates (TFRs) since the 19th century. Generally speaking, decreases in differential fertility and mortality have meant that there is less opportunity for natural selection to eliminate deleterious mutations from the human gene pool. It has been argued that the average human may carry ~250–300 mutations that are mostly deleterious, as well as several hundred less-deleterious variants. These deleterious alleles in extant humans mean that our fitness is being constrained. While such alleles are viewed as reducing human fitness, they may also have had an adaptive function in the past, such as assisting in genetic complexity, sexual recombination and diploidy. Saying this, our current knowledge on these fitness compromising alleles is still lacking.

scholarly journals The nature of nurture in a wild mammal's fitness

2015 ◽  
Vol 282 (1806) ◽  
pp. 20142422 ◽  
Author(s):  
S. Eryn McFarlane ◽  
Jamieson C. Gorrell ◽  
David W. Coltman ◽  
Murray M. Humphries ◽  
Stan Boutin ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Natural Selection ◽  
Maternal Effects ◽  
Adaptive Evolution ◽  
Genetic Effects ◽  
Adaptive Potential ◽  
Red Squirrels ◽  
Trade Offs ◽  
The Face ◽  
North American Red Squirrels

Genetic variation in fitness is required for the adaptive evolution of any trait but natural selection is thought to erode genetic variance in fitness. This paradox has motivated the search for mechanisms that might maintain a population's adaptive potential. Mothers make many contributions to the attributes of their developing offspring and these maternal effects can influence responses to natural selection if maternal effects are themselves heritable. Maternal genetic effects (MGEs) on fitness might, therefore, represent an underappreciated source of adaptive potential in wild populations. Here we used two decades of data from a pedigreed wild population of North American red squirrels to show that MGEs on offspring fitness increased the population's evolvability by over two orders of magnitude relative to expectations from direct genetic effects alone. MGEs are predicted to maintain more variation than direct genetic effects in the face of selection, but we also found evidence of maternal effect trade-offs. Mothers that raised high-fitness offspring in one environment raised low-fitness offspring in another environment. Such a fitness trade-off is expected to maintain maternal genetic variation in fitness, which provided additional capacity for adaptive evolution beyond that provided by direct genetic effects on fitness.

scholarly journals Hormone-mediated suites as adaptations and evolutionary constraints

2007 ◽  
Vol 363 (1497) ◽  
pp. 1611-1620 ◽  
Author(s):  
Joel W McGlothlin ◽  
Ellen D Ketterson
Keyword(s):  
Natural Selection ◽  
Adaptive Evolution ◽  
Evolutionary Constraints ◽  
Empirical Methods ◽  
Dual Roles ◽  
Genetic Theory ◽  
Correlated Traits ◽  
Male And Female ◽  
Quantitative Genetic ◽  
Future Work

Hormones mediate the expression of suites of correlated traits and hence may act both to facilitate and constrain adaptive evolution. Selection on one trait within a hormone-mediated suite may, for example, lead to a change in the strength of the hormone signal, causing either beneficial or detrimental changes in correlated traits. Theory and empirical methods for studying correlated trait evolution have been developed by the field of evolutionary quantitative genetics, and here we suggest that their application to the study of hormone-mediated suites may prove fruitful. We present hypotheses for how selection shapes the evolution of hormone-mediated suites and argue that correlational selection, which arises when traits interact in their effects on fitness, may act to alter or conserve the composition of hormone-mediated suites. Next, we advocate using quantitative genetic methods to assess natural covariation among hormone-mediated traits and to measure the strength of natural selection acting on them. Finally, we present illustrative examples from our own work on the evolution of testosterone-mediated suites in male and female dark-eyed juncos. We conclude that future work on hormone-mediated suites, if motivated by quantitative genetic theory, may provide important insights into their dual roles as adaptations and evolutionary constraints.

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