Search results for "selection"

Local old olive landrace varieties in Israel—Valuable plant genetic resources in olive cultivation

2008

It is assumed that the cultivation of olive trees started in the East Mediterranean in the third millennia BCE. Throughout history and until recently, successful olive clones were maintained vegetatively and were grafted either on seedlings or on spheroblasts removed from the base of the trunk. It therefore can be hypothesized that local old olive trees, older than 500 years might represent an ancient gene pool. Modern terminology categorizes local genotypes into four main variety groups. However, in traditional terminology these were further differentiated into 27 cultivars according to their phenotypic traits. This genetic diversity, along with the fact that olive trees have been cultivat…

Estimation Of The Genetic Parameters Of Eight Soybean Varieties In The Wasegi Village At Prafi District Manokwari Regency

2020

This study aims to estimate genetic parameters including genetic diversity coefficient, phenotypic diversity coefficient, heritability value, and the correlation between the character of plants from eight soybean varieties. The research was conducted from August to December 2017, in the Wasafi Village of Prafi District, Manokwari Regency. The study was designed using Randomized Block Design (RBD) with 8 treatments of soybean varieties. Each treatment was repeated 4 times, to obtain 32 experimental units. The data obtained were analyzed using ANOVA and if it had a significant effect, it was further tested using the Duncan Multiple Range Test (DMRT) at the 95% level, through the Costat progra…

Genetic Diversity and Evolution of Viral Populations

2021

Abstract Population genetic diversity plays a prominent role in viral evolution, pathogenesis, immune escape, and drug resistance. Different mechanisms are responsible for creating and maintaining genetic diversity in viruses, including error-prone replication, repair avoidance, and genome editing, among others. This diversity is subsequently modulated by natural selection and random genetic drift, whose action in turn depends on multiple factors including viral genetic architecture, viral demography, and ecology. Understanding these processes should contribute to the development of more efficient control and treatment strategies against viral pathogens.

On the Parameterization of Cartesian Genetic Programming

2020

In this work, we present a detailed analysis of Cartesian Genetic Programming (CGP) parametrization of the selection scheme ($\mu+\lambda$), and the levels back parameter l. We also investigate CGP’s mutation operator by decomposing it into a self-recombination, node function mutation, and inactive gene randomization operators. We perform experiments in the Boolean and symbolic regression domains with which we contribute to the knowledge about efficient parametrization of two essential parameters of CGP and the mutation operator.

2006

Understanding evolutionary processes that drive genome reduction requires determining the tempo (rate) and the mode (size and types of deletions) of gene losses. In this study, we analysed five endosymbiotic genome sequences of the gamma-proteobacteria (three different Buchnera aphidicola strains, Wigglesworthia glossinidia, Blochmannia floridanus) to test if gene loss could be driven by the selective importance of genes. We used a parsimony method to reconstruct a minimal ancestral genome of insect endosymbionts and quantified gene loss along the branches of the phylogenetic tree. To evaluate the selective or functional importance of genes, we used a parameter that measures the level of ad…

Frequency-dependent selection in human immunodeficiency virus type 1.

2001

Genetic variation is the main evolutionary strategy adopted by RNA viruses and retroviruses. Evolution operates through competition between different individuals in the same environment, resulting in the imposition of the fittest variant. The process of competition could be affected by various factors, including the frequency of the different competing individuals. In order to investigate this aspect, individual virus populations derived from a human immunodeficiency virus type 1 isolate were studied at different competing proportions. The dynamics of variant imposition in each competition experiment permitted the detection of frequency-dependent selection (FDS); i.e. the imposition of vari…

Multiple paternity and mating group size in the European earwig,Forficula auricularia

2014

The patterns of multiple paternity among the progeny of females are key properties of genetic mating systems. Female multiple mating should evolve due to direct or indirect benefits, but it may also partly be driven by the encounter rate with different potential mates. 2. In this study this hypothesis was experimentally tested in the European earwig (Forficula auricularia L.) by establishing experimental mating groups that differed in the number of males and females (i.e. density). The number of sires and mean sibling relatedness in each clutch were estimated using microsatellite-based paternity analysis. 3. As predicted, the mean number of sires per clutch was significantly increased, and …

Accelerated Evolution of Fetuin-A (FETUA, also AHSG) is Driven by Positive Darwinian Selection, not GC-Biased Gene Conversion

2009

article i nfo Human Fetuin-A (FETUA, also termed AHSG) is a serum protein composed of two cystatin-like domains D1 and D2 of together 235 amino acids (aa) and an unrelated domain D3 of 114 aa. Though the protein plays a role in diverse physiological and pathological processes, comparably little is known about sequence evolution of FETUA. We therefore analyzed its molecular evolution on the basis of coding sequences of 16 primate species. Ratios of non-synonymous to synonymous substitution rates (dn/ds= ω) suggest that a previously reported acceleration of sequence evolution of exon 7, which encodes domain D3, is driven by positive selection instead of neutral evolution. Irrespective of the …

Evolution of small prokaryotic genomes

2015

As revealed by genome sequencing, the biology of prokaryotes with reduced genomes is strikingly diverse. These include free-living prokaryotes with ∼800 genes as well as endosymbiotic bacteria with as few as ∼140 genes. Comparative genomics is revealing the evolutionary mechanisms that led to these small genomes. In the case of free-living prokaryotes, natural selection directly favored genome reduction, while in the case of endosymbiotic prokaryotes neutral processes played a more prominent role. However, new experimental data suggest that selective processes may be at operation as well for endosymbiotic prokaryotes at least during the first stages of genome reduction. Endosymbiotic prokar…

EFFECT OF DELETERIOUS MUTATION-ACCUMULATION ON THE FITNESS OF RNA BACTERIOPHAGE MS2

2000

RNA viruses show the highest mutation rate in nature. It has been extensively demonstrated that, in the absence of purifying selection, RNA viruses accumulate deleterious mutations at a high rate. However, the parameters describing this accumulation are, in general, poorly understood. The present study reports evidences for fitness declines by the accumulation of deleterious mutations in the bacteriophage MS2. We estimated the rate of fitness decline to be as high as 16% per bottleneck transfer. In addition, our results agree with an additive model of fitness effects.