scholarly journals Natural selection promotes the evolution of recombination 1: among selected genotypes

2021 ◽  
Author(s):  
Philip J Gerrish ◽  
Benjamin J Galeota-Sprung ◽  
Paul D. Sniegowski ◽  
Julien Chevallier ◽  
Bernard Ycart
Keyword(s):  
Natural Selection ◽  
Genetic Material ◽  
Offspring Fitness ◽  
Break Up ◽  
New Perspective

Shuffling one's genetic material with another individual seems a risky endeavor more likely to decrease than to increase offspring fitness. This intuitive argument is commonly employed to explain why the ubiquity of sex and recombination in nature is enigmatic. It is predicated on the notion that natural selection assembles selectively well-matched combinations of genes that recombination would break up resulting in low-fitness offspring -- a notion so intuitive that it is often stated in the literature as a self-evident premise. We show, however, that this common premise is only self evident on the surface and that, upon closer examination, it is fundamentally flawed: we find that natural selection in fact has an encompassing tendency to assemble selectively mismatched combinations of alleles; recombination breaks up these selectively mismatched combinations (on average), assembles selectively matched combinations, and should thus be favored. The new perspective our findings offer suggests that sex and recombination are not so enigmatic but are instead natural and unavoidable byproducts of natural selection.

Advances in the Brazilian animal genetic resources conservation programme

1999 ◽  
Vol 25 ◽  
pp. 107-121 ◽  
Author(s):  
A. da S. Mariante ◽  
M. do S.M. Albuquerque ◽  
A. A. do Egito ◽  
C. McManus
Keyword(s):  
Natural Selection ◽  
Genetic Resources ◽  
Agricultural Research ◽  
National Level ◽  
Genetic Material ◽  
Genetic Distances ◽  
Ex Situ ◽  
Research Centre ◽  
Conservation Programme ◽  
Resources Conservation

SummaryBrazil has various species of domestic animals which developed from breeds brought by the Portuguese settlers soon after the discovery. Over the last five centuries, these breeds have been submitted to natural selection in particular environments and therefore today, they present characteristics adapted to the specific environmental conditions. From the beginning of this century, some exotic breeds, selected in temperate regions, have begun to be imported. Although more productive, these breeds lack adaptation traits, such as resistance to disease and parasites found in breeds considered to be“native” but even so, little by little, they have substituted the native breeds to such an extent that the latter are, today, in danger of extinction. To avoid the loss of this important genetic material, Brazil created an Animal Genetics Resource Conservation Programme, coordinated by the National Research Centre for Genetic Resources and Biotechnology (Cenargen) of the Brazilian Agricultural Research Corporation (EMPRAPA). The conservation has been carried out by various Research Centres of EMPRAPA, Universities, State Research Corporations, as well as by private farmers, with a single coordinator at national level, Cenargen. The conservation is being carried out through Conservation Nuclei, situated in the habitats where the animals have been subjected to natural selection (in situ), and by the storage of semen and embryos (ex situ). The recently created Animal Genetics Laboratory of Cenargen allowed genetic characterisation studies on cattle and horse breeds to begin, and, in the near future, work with asses, buffalo and sheep will be conducted‥ From the results of this research it will be possible to compare the native breeds and estimate genetic distances between them. The harmonisation of chosen micro-satellites with those which have been used in other Latin America and Iberian Peninsula countries will be extremely useful for comparative studies and will allow future exchange of germplasm between countries.

scholarly journals Modelling for the Inheritance of Endangered Equid Multiple Births and Fertility: Determining Risk Factors and Genetic Parameters in Donkeys (Equus asinus)

2018 ◽  
Author(s):  
Francisco Javier Navas González ◽  
Jordi Jordana Vidal ◽  
Amy Katherine McLean ◽  
José Manuel León Jurado ◽  
Cecilio José Barba Capote ◽  
...  
Keyword(s):  
Fixed Effects ◽  
Genetic Parameters ◽  
Genetic Material ◽  
Multiple Births ◽  
Multiple Birth ◽  
Birth Season ◽  
Equus Asinus ◽  
Frozen Semen ◽  
Reproductive Techniques ◽  
New Perspective

Multiple births or twinning in equids are dangerous, undesirable situations that compromise the life of the dam and resulting offspring. However, embryo vitrification and freezing techniques take advantage of individuals whose multiple ovulations allow flushing more fertilised embryos from the oviduct to be collected, increasing the productivity and profitability of such techniques. Embryo preservation is especially important in highly endangered populations such as certain donkey (Equus asinus) breeds; for which conventional reproductive techniques have previously failed. For instance, becoming an effective alternative to artificial insemination with frozen semen to preserve the individuals’ genetic material. The objective of this study was to examine the historical foaling records of Andalusian donkeys to estimate genetic parameters for multiple births, assessing the historical foal number born per animal, maximum foal number per birth and multiple birth number per animal. We designed an Animal Model with single records considering the fixed effects of birthyear, birth season, sex, farm, and husbandry system, and age as a linear and quadratic covariate. Restricted maximum likelihood reported heritability estimates ranging from 0.18±0.01 to 0.24±0.01. Genetic and phenotypic correlations ranged from 0.01±0.01 to 0.83±0.01 and 0.12±0.01 and 0.53±0.01, respectively. These estimates enable the potential for selection against/for these traits, offering a new perspective for donkey breeding and conservation.

scholarly journals Natural selection and the advantage of recombination

2020 ◽  
Author(s):  
Philip Gerrish ◽  
Benjamin Galeota-Sprung ◽  
Fernando Cordero ◽  
Paul Sniegowski ◽  
Alexandre Colato ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Natural Selection ◽  
Genetic Material ◽  
Great Difficulty ◽  
Vantage Point ◽  
Evolution Of Sex ◽  
Fitness Effects ◽  
Living Things ◽  
Additive Component ◽  
Do So

Abstract Exchanging genetic material with another individual seems risky from an evolutionary standpoint, and yet living things across all scales and phyla do so quite regularly. The pervasiveness of such genetic exchange, or recombination, in nature has defied explanation since the time of Darwin. Conditions that favor recombination, however, are well-understood: recombination is advantageous when the genomes of individuals in a population contain more selectively mismatched combinations of alleles than can be explained by chance alone. Recombination remedies this imbalance by shuffling alleles across individuals. The great difficulty in explaining the ubiquity of recombination in nature lies in identifying a source of this imbalance that is comparably ubiquitous. Intuitively, it would seem that natural selection should reduce the imbalance by favoring selectively matched combinations of high-fitness alleles, thereby opposing the evolution of recombination. We show, however, that this intuition is wrong; to the contrary, we find that natural selection has an encompassing tendency to assemble selectively mismatched combinations of alleles (the products of natural selection), thereby increasing the imbalance and promoting the evolution of recombination. We further show that population dynamics that lead to the fixation of these selectively mismatched genotypes (the process of natural selection) themselves produce an average imbalance that promotes the evolution of recombination. This fact is completely independent of the distribution of allelic fitness effects and is primarily due to the additive component of those effects. Our findings provide a novel vantage point from which the enormous body of established work on the evolution of sex and recombination may be viewed anew. They further suggest that recombination evolved and is maintained more as an unavoidable byproduct of natural selection than as a catalyst.

Antitypes, Ancestors, and the Origin of Modern Giraffes

2021 ◽  
pp. 85-120
Author(s):  
Graham Mitchell
Keyword(s):  
Climate Change ◽  
Natural Selection ◽  
East Africa ◽  
Central Europe ◽  
North Africa ◽  
Genetic Material ◽  
Giraffa Camelopardalis ◽  
Southern Central ◽  
Genetic Pool ◽  
Unique Species

Against the odds, over a period of 8 million years the genetic material in small gazelle-like Canthumerycids transformed by natural selection into modern long-legged, long-necked giraffes, Giraffa camelopardalis. How did that happen? The 8 million-year-long evolutionary gap between Canthumerycids and giraffes, during which the astonishing morphophysiological changes occurred, is filled by three ancestral species of Paleotragine giraffids—Giraffokeryx, Paleotragus, and Samotherium—that lived in southern central Europe, with each making small but significant evolutionary contributions. While all had elongated necks, their necks were never more than half the length of modern giraffes. All, though, had long legs. Long necks arose in Bohlinia, a unique species that evolved from the Paleotragine genetic pool. Bohlinia migrated to Asia and gave rise to Indian and Chinese giraffes, and also into North Africa. Relatively quickly the Indo-Asian giraffes became extinct. In Africa the giraffe lineage that produced modern giraffes began with the evolution of Giraffa jumae from Bohlinia about 6 million years ago. G. jumae was the origin of three ancestors of modern giraffes—G. stillei, G. gracilis, and G. pygmaea—that made their appearance in East Africa around 3 million years ago. Their appearance then was a consequence of major episodes of climate change. From their genetic pool, modern giraffes, G. camelopardalis, emerged 1 million years ago.

A SURVEY OF GENETICS AS IT APPLIES TO PROBLEMS IN MEDICINE

PEDIATRICS ◽  
1957 ◽  
Vol 20 (1) ◽  
pp. 177-218
Keyword(s):  
Natural Selection ◽  
Genetic Material ◽  
Well Being ◽  
Heritable Variation ◽  
The Past ◽  
Environmental Requirements ◽  
The Subject ◽  
The Individual ◽  
The Impact ◽  
Source Of Information

GENETICS is the study of heritable variation. The ultimate form the organism takes, its phenotype, is the result of environmental influences imposed upon the potentialities determined by the inherited genetic material, the genotype. Since the inherited capacities are fixed at the time of fertilization and in general do not change throughout the life of the organism, while the environment is ever variable, the study of genetics cannot help but offer an important source of information concerning biological mechanisms. The impact of genetics upon medicine has not been very great in the past, but an increasing interest in the metabolic aspects of disease has led to a recognition of the genetic control of such processes, and it is probable that in the future this subject will become increasingly important. The civilization of man has been exemplified by an increasing concern with the preservation of the life and well-being of individuals, and physicians have emerged as an agency for the counteraction of the action of natural selection. Natural selection may be visualized as limiting extravagant variation, while conserving the latent capacity to vary according to changing environmental requirements. In medicine we seek ways to alter the environment for particular individuals so as to increase and preserve their ability to survive and to reproduce, thereby maintaining variants which might be otherwise eliminated. The contribution to biological variability of the genetic material has been the subject of much study, and it has been pointed out that the favorable or unfavorable selective value of particular genes may best be expressed in terms of their influence upon the ability of the individual to reproduce.

scholarly journals On the evolutionary adjustment of spontaneous mutation rates

1967 ◽  
Vol 9 (1) ◽  
pp. 23-34 ◽  
Author(s):  
Motoo Kimura
Keyword(s):  
Population Genetics ◽  
Natural Selection ◽  
Mutation Rate ◽  
Spontaneous Mutation ◽  
Genetic Material ◽  
Genetic Load ◽  
Mutation Rates ◽  
Spontaneous Mutation Rate ◽  
Physiological Limit ◽  
Present Mode

Evolutionary factors which tend to decrease the mutation rate through natural selection and those which tend to increase the mutation rate are discussed from the standpoint of population genetics. The author's theory of optimum mutation rate based on the principle of minimum genetic load is re-examined, assuming that mutation rate is adjusted in the course of evolution in such a way that the sum of mutational and substitutional load is minimized. Another hypothesis is also examined that only selection toward lowering the mutation rate is effective and the present mutation rate in each organism represents the physical or physiological limit that may be attained by natural selection.The possibility cannot be excluded that the spontaneous mutation rate is near the minimum that may be attained under the present mode of organization of the genetic material, and at the same time is not very far from the optimum in the sense of minimizing the genetic load.

scholarly journals ¿Pierre Bourdieu era “bachelardiano”? / Was Pierre Bourdieu "Bachelardian"?

2020 ◽  
Vol 5 (25) ◽  
pp. 157-168
Author(s):  
Marc Joly ◽  
Sergio Lorenzo Sandoval Aragón
Keyword(s):  
Philosophy Of Science ◽  
Pierre Bourdieu ◽  
Gaston Bachelard ◽  
Break Up ◽  
New Perspective ◽  
The Relationship

En este artículo se analiza críticamente la relación de la epistemología de Gastón Bachelard y la sociología de Pierre Bourdieu. En la primera parte del artículo, se analiza la lectura de la epistemología en Bourdieu que lleva a cabo el antropólogo Denis Baranger quien, inspirado en la filosofía de la ciencia de Jean-Claude Passeron, la caracteriza como estrictamente “bachelardiana”, lo que impide comprender la naturaleza del concepto de reflexividad, central en la sociología de Pierre Bourdieu. En la segunda parte, se sostiene que, al abordar la relación de la epistemología de Gastón Bachelard y la sociología de Pierre Bourdieu desde una perspectiva procesual o genética, es posible describir el trayecto seguido por Bourdieu que va de un uso de la epistemología bachelardiana para justificar la sociología como ciencia de las prácticas, a la construcción de esta ciencia como la base de una epistemología general reestructurada. Este trayecto se caracteriza como una sociologización de la epistemología de Bachelard, por lo tanto, como una ruptura con el régimen conceptual “filosófico”. Se concluye, a la luz de esta nueva perspectiva, que la lectura de Baranger es insuficiente para comprender la epistemología de Bourdieu y todas sus implicaciones, particularmente su contribución a la constitución del paradigma sociológico. This article critically analyzes the relationship between Gaston Bachelard’s epistemology and Pierre Bourdieu’s so-ciology. The first part of the article analyzes Bourdieu’s reading of epistemology by the anthropologist Denis Ba-ranger who, inspired by Jean-Claude Passeron’s philosophy of science, characterizes it as strictly “Bachelardian”, which prevents understanding the nature of the concept of reflexivity, central to the sociology of Pierre Bourdieu. In the second part, it is argued that, when dealing with the relationship between Gaston Bachelard’s epistemology and Pierre Bourdieu’s sociology from a processual or genetic perspective, it is possible to describe the trajectory followed by Bourdieu that goes from a use of Bachelard’s epistemology to justify sociology as a science of practice, to the construction of this science as the basis of a general restructured epistemology. This is characterized as a sociologization of Bachelard’s epistemology, therefore, as a break up with the conceptual “philosophical” regime. In light of this new perspective, it is concluded that Baranger’s reading is insufficient to understand Bourdieu’s episte-mology and all its implications, particularly its contribution to the constitution of the sociological paradigm.

scholarly journals Origin, genetic diversity and evolution of Andaman local duck, a native duck germplasm of an insular region of India

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0245138
Author(s):  
Arun Kumar De ◽  
Sneha Sawhney ◽  
Debasis Bhattacharya ◽  
T. Sujatha ◽  
Jai Sunder ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Natural Selection ◽  
Environmental Changes ◽  
Genetic Material ◽  
Southeast Asian ◽  
Conservation Strategy ◽  
Asian Countries ◽  
High Genetic Diversity ◽  
D Loop ◽  
Southeast Asian Countries

Domestic ducks are of paramount importance as a cheap source of protein in rural India. Andaman local duck (ALD) is an indigenous avian genetic resource of Andaman and Nicobar islands (ANI) and is mainly distributed in Middle and Northern parts of these islands. Negligence has brought this breed on the edge of extinction necessitating immediate conservation efforts. Here, we report the genetic diversity, population structure and matrilineal genetic root of ALD. Partial mtDNA D-loop sequences were analyzed in 71 ALD samples and analysis revealed 19 polymorphic sites and 13 haplotypes. Estimated haplotype (Hd ± SD) and nucleotide diversity (π ± SD) were 0.881 ± 0.017 and 0.00897 ± 0.00078 respectively. The high genetic diversity of ALD indicates introgression of genetic material from other local duck breeds. In addition, it can be postulated that ALD bearing high genetic diversity has strong ability to adapt to environmental changes and can withstand impending climate change. Phylogenetic and network analysis indicate that ALD falls under Eurasian clade of mallard and ALD forms three clusters; one cluster is phylogenetically close to Southeast Asian countries, one close to Southern part of mainland India and the third one forms an independent cluster. Therefore, ALD might have migrated either from Southeast Asian countries which enjoy a close cultural bondage with ANI from time immemorial or from Southern part of India. The independent cluster may have evolved locally in these islands and natural selection pressure imposed by environmental conditions might be the driving force for evaluation of these duck haplotypes; which mimics Darwin’s theory of natural selection. The results of the study will be beneficial for formulating future breeding programme and conservation strategy towards sustainable development of the duck breed.

SREM observation of the interaction between the in-situ deposited Pd small particles and MgO cleavage surface

1986 ◽  
Vol 44 ◽  
pp. 382-383
Author(s):  
H.-J. Ou
Keyword(s):  
Electron Microscopy ◽  
Small Particle ◽  
Small Particles ◽  
Cleavage Surface ◽  
Metallic Particles ◽  
Microscopy Technique ◽  
Ceramic Surfaces ◽  
Reflection Electron Microscopy ◽  
New Perspective

The understanding of the interactions between the small metallic particles and ceramic surfaces has been studied by many catalyst scientists. We had developed Scanning Reflection Electron Microscopy technique to study surface structure of MgO hulk cleaved surface and the interaction with the small particle of metals. Resolutions of 10Å has shown the periodic array of surface atomic steps on MgO. The SREM observation of the interaction between the metallic particles and the surface may provide a new perspective on such processes.

Sign in / Sign up

Export Citation Format

Share Document