scholarly journals Interaction of selection and recombination in the fixation of negative-epistatic genes

1996 ◽  
Vol 67 (3) ◽  
pp. 257-269 ◽  
Author(s):  
Yannis Michalakis ◽  
Montgomery Slatkin
Keyword(s):  
Double Mutant ◽  
Static Model ◽  
The Other ◽  
Relative Importance ◽  
Selection Intensity ◽  
Recombination Rates ◽  
Epistatic Interactions ◽  
Evolutionary Transitions ◽  
Negative Epistasis ◽  
Probability Of Fixation

SummaryWe investigated the interaction of recombination and selection on the process of fixation of two linked loci with epistatic interactions in fitness. We consider both the probability of fixation of newly arising mutants (the static model) and the time to fixation under continued mutation (the dynamic model). Our results show that the fixation of a new advantageous combination is facilitated by higher fitness of the advantageous genotype and by weaker selection against the intermediate deleterious genotypes. Fixation occurs more rapidly when the recombination rates are small, except when selection against intermediate genotypes is weak and selection in favour of the double mutant is very strong. In these cases fixation is more rapid when the recombinant rate is large. Mutations of strong effects, deleterious when alone but beneficial when coupled, are fixed more easily than mutations of intermediate effects, at least for large recombination rates. Among the possible pathways the process of fixation might follow, independent substitutions lead to the fixation of the double mutant only when selection is weak. The relative importance of the other pathways depends on the interaction between recombination and selection. The coupled-gamete pathway (i.e. when the population waits until the double mutant appears and then drives it to fixation) is more important as selection intensity increases and the recombination rate is reduced. For all recombination rates, asymmetries in fitness of the intermediate genotypes increase the rate at which fixations occur. Finally, throughout the fixation process, the population will be monomorphic at least at one of the two loci for most of the time, which implies that there would be little opportunity to detect the presence of negative epistasis even if it were important for occasional evolutionary transitions.

scholarly journals The effect of epistasis on sexually antagonistic genetic variation

2014 ◽  
Vol 281 (1787) ◽  
pp. 20140489 ◽  
Author(s):  
Göran Arnqvist ◽  
Nikolas Vellnow ◽  
Locke Rowe
Keyword(s):  
Genetic Variation ◽  
Parameter Space ◽  
Genetic Variance ◽  
The Other ◽  
Population Divergence ◽  
Wild Populations ◽  
Epistatic Interactions ◽  
Locus Model ◽  
Males And Females ◽  
Negative Epistasis

There is increasing evidence of segregating sexually antagonistic (SA) genetic variation for fitness in laboratory and wild populations, yet the conditions for the maintenance of such variation can be restrictive. Epistatic interactions between genes can contribute to the maintenance of genetic variance in fitness and we suggest that epistasis between SA genes should be pervasive. Here, we explore its effect on SA genetic variation in fitness using a two locus model with negative epistasis. Our results demonstrate that epistasis often increases the parameter space showing polymorphism for SA loci. This is because selection in one locus is affected by allele frequencies at the other, which can act to balance net selection in males and females. Increased linkage between SA loci had more marginal effects. We also show that under some conditions, large portions of the parameter space evolve to a state where male benefit alleles are fixed at one locus and female benefit alleles at the other. This novel effect of epistasis on SA loci, which we term the ‘equity effect’, may have important effects on population differentiation and may contribute to speciation. More generally, these results support the suggestion that epistasis contributes to population divergence.

Exploration of Product Centric Factors in Telecom Industry

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Swati Ganeti ◽  
Rajat Agarwal ◽  
Murali Krishna Medudula ◽  
Mahim Sagar
Keyword(s):  
Service Quality ◽  
Service Provider ◽  
Service Providers ◽  
Network Connectivity ◽  
Factor Loading ◽  
The Other ◽  
Relative Importance ◽  
Network Connection ◽  
Telecom Service ◽  
Telecom Industry

Telecom industry is one of those industries which has changed dramatically during the past decade. With more and more players entering in this industry, competition is ever increasing. The war between these players is slowly shifting from the price to the augmentation. This paper aims at exploring such factors which influence a customers preference of one telecom service provider (TSP) over the other. It is a descriptive research where study has been conducted among the consumers of different telecom service providers (TSPs). By reviewing the existing literature in this domain, we explored different factors which affect the consumers decision to prefer one telecom service provider over the other. A consumer targeted questionnaire was designed where consumers were asked about the factors they consider (with their relative importance quantified using Likert scale), before buying a new network connection to know the relative importance of the various factors. Factor Analysis was performed to club various variables into distinct factors. Statistical techniques then helped in identifying the relative importance. From the Factor Loading matrix the following five factors were generated:- Overall service quality, Point of Purchase Differentiator, Promotion Measures, Tariff Plans and Size of the Network. Further study in the behavioural perceptions of consumer shows that the most important factor in influencing the customer buying behavior is Service Quality. The second most important factor is cost and various plans offered by the telecom service provider. Network connectivity was considered by almost all the respondents and consumers prefer the largest network player. The study also found that promotional measures dont influence the customers as expected.

SPT10 and SPT21 are required for transcription of particular histone genes in Saccharomyces cerevisiae

1994 ◽  
Vol 14 (8) ◽  
pp. 5223-5228
Author(s):  
C Dollard ◽  
S L Ricupero-Hovasse ◽  
G Natsoulis ◽  
J D Boeke ◽  
F Winston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Differential Expression ◽  
Double Mutant ◽  
The Other ◽  
Histone Genes ◽  
Related Gene ◽  
Histone Proteins ◽  
Histone Locus

The Saccharomyces cerevisiae genome contains four loci that encode histone proteins. Two of these loci, HTA1-HTB1 and HTA2-HTB2, each encode histones H2A and H2B. The other two loci, HHT1-HHF1 and HHT2-HHF2, each encode histones H3 and H4. Because of their redundancy, deletion of any one histone locus does not cause lethality. Previous experiments demonstrated that mutations at one histone locus, HTA1-HTB1, do cause lethality when in conjunction with mutations in the SPT10 gene. SPT10 has been shown to be required for normal levels of transcription of several genes in S. cerevisiae. Motivated by this double-mutant lethality, we have now investigated the interactions of mutations in SPT10 and in a functionally related gene, SPT21, with mutations at each of the four histone loci. These experiments have demonstrated that both SPT10 and SPT21 are required for transcription at two particular histone loci, HTA2-HTB2 and HHF2-HHT2, but not at the other two histone loci. These results suggest that under some conditions, S. cerevisiae may control the level of histone proteins by differential expression of its histone genes.

scholarly journals Fertility and its relation to social conditions A study of the vital statistics of London in 1930–1932

1937 ◽  
Vol 37 (1) ◽  
pp. 108-123 ◽  
Author(s):  
K. Mitra
Keyword(s):  
Birth Rate ◽  
Western Europe ◽  
Vital Statistics ◽  
Considerable Extent ◽  
The Other ◽  
Rapid Decline ◽  
Relative Importance ◽  
Absolute Size ◽  
The Military

The rapid decline of the birth-rate in nearly all countries of western Europe has naturally attracted much attention. Some have studied the probable effects upon the absolute size and the age constitution of the population, and the consequence entailed upon the military and economic strength of a nation. Others have drawn attention to resulting change's in the relative importance of diseases of young, adult and old ages. Changes in mere numbers depend wholly, and the other changes to a considerable extent, upon quantitative factors; they must occur even if the quality of those born differs in no way from that of those produced when fertility was at a higher level. But, if the quality of births changes with their quantity, then the consequences of decrease of numbers may be better or worse than mere numerical changes would involve.

scholarly journals KNOX HOMOLOGS SHOOT MERISTEMLESS (STM) and KNAT6 are epistatic to CLAVATA3 (CLV3) during embryonic meristem development in Arabidopsis thaliana

2020 ◽  
Author(s):  
Sharma Nidhi ◽  
Liu Tie
Keyword(s):  
Arabidopsis Thaliana ◽  
Shoot Apex ◽  
Double Mutant ◽  
Genetic Interaction ◽  
Homeobox Gene ◽  
The Other ◽  
Shoot Meristem ◽  
Published Data ◽  
Meristem Development ◽  
Shoot Meristemless

AbstractIn Arabidopsis, the genes SHOOT MERISTEMLESS (STM) and CLAVATA3 (CLV3) antagonistically regulate shoot meristem development. STM is essential for both development and maintenance of the meristem, as stm mutants fail to develop a shoot meristem during embryogenesis. CLV3, on the other hand, negatively regulates meristem proliferation, and clv3 mutants possess an enlarged shoot meristem. Genetic interaction studies revealed that stm and clv3 dominantly suppress each other’s phenotypes. STM works in conjunction with its closely related homologue KNOTTED1-LIKE HOMEOBOX GENE 6 (KNAT6) to promote meristem development and organ separation, as stm knat6 double mutants fail to form a meristem and produce a fused cotyledon. In this study, we show that clv3 fails to promote post-embryonic meristem formation in stm-1 background if we also remove KNAT6. stm-1 knat6 clv3 triple mutants result in early meristem termination and produce fused cotyledons similar to stm knat6 double mutant. Notably, the stm-1 knat6 and stm-1 knat6 clv3 alleles lack tissue in the presumed region of SAM. stm knat6 clv3 also showed reduced inflorescence size and shoot apex size as compared to clv3 single or stm clv3 double mutants. In contrast to previously published data, these data suggest that stm is epistatic to clv3 in postembryonic meristem development.HighlightSTM and KNAT6 genes determine post-embryonic meristem formation and activity in Arabidopsis. clv3 mutation is unable to rescue the stm knat6 meristemless phenotype.

scholarly journals Estructura de preferencias de los consumidores de vino y actitudes hacia los vinos con denominación de origen. El caso de Castilla-La Mancha

2011 ◽  
Vol 5 (9) ◽  
pp. 57 ◽  
Author(s):  
R. Bernabéu ◽  
M. Olmeda ◽  
M. Díaz
Keyword(s):  
Consumer Preferences ◽  
The Other ◽  
Consumer Attitude ◽  
Relative Importance ◽  
La Mancha ◽  
The One

This paper covers a dual objective. On the one hand, the relative importance was determined of the wine attributes that influence the formation of consumer preferences in Castilla-La Mancha. On the other, consumer attitude was analysed towards wine with Castilla-La Mancha’s most important Designation of Origin (D.O.) certifications (D.O. La Mancha and D.O. Valdepeñas), compared with the best-known wine in the national ambit (D.O. Rioja). As a result of the first objective, the most relevant attributes are price, colour (red, white), certification and origin, in this order. The second objective shows that D.O. La Mancha and D.O. Valdepeñas are considered cheaper wines, of habitual consumption and a lower prestige image, while D.O. Rioja wines are seen as prestigious and expensive, so their consumption is considered appropriate for special occasions.

scholarly journals On the Mechanism of Protection against Infective Disease

1928 ◽  
Vol 28 (2) ◽  
pp. 127-132
Author(s):  
M. Greenwood ◽  
E. M. Newbold ◽  
W. W. C. Topley ◽  
J. Wilson
Keyword(s):  
The Other ◽  
Relative Importance ◽  
Selective Mortality ◽  
Lethal Infection ◽  
Infective Disease ◽  
Subsequent Exposure ◽  
The Subject ◽  
The One

In the course of a paper by the present writers (this Journal, xxv, 336–53) an attempt was made to assess the relative importance of selective mortality on the one hand and sub-lethal infection on the other in increasing herd resistance to subsequent exposure to infection. The subject was further considered by one of us (E.M.N.) in a later report (this Journal, xxvi, 19–27).

scholarly journals Inositol phosphate release and steroidogenesis in rat adrenal glomerulosa cells. Comparison of the effects of endothelin, angiotensin II and vasopressin

1990 ◽  
Vol 271 (3) ◽  
pp. 791-796 ◽  
Author(s):  
E A Woodcock ◽  
P J Little ◽  
J K Tanner
Keyword(s):  
Angiotensin Ii ◽  
Metabolic Pathways ◽  
Inositol Phosphate ◽  
The Other ◽  
Relative Importance ◽  
Phosphate Release ◽  
Phosphatidylinositol Turnover ◽  
Transient Rise ◽  
Glomerulosa Cells ◽  
Stimulation Of

Endothelin has steroidogenic activity in adrenal glomerulosa cells, as do two other vasoconstrictor peptides, angiotensin II and vasopressin. The steroidogenic activities of angiotensin II and vasopressin are probably mediated via the phosphatidylinositol-turnover pathway and associated changes in cytosolic Ca2+ concentration. Endothelin caused a steroidogenic response, which was small compared with that to angiotensin II and quantitatively similar to the vasopressin response. Cytosolic free Ca2+ responses were similarly higher to angiotensin II than to either of the other two peptides. However, total inositol phosphate responses to endothelin and angiotensin II were similar when these were measured over 20 min, and were quantitatively greater than the vasopressin response. A detailed study has been made of the phosphatidylinositol-turnover response to endothelin in comparison with responses to angiotensin II and vasopressin. Each of the three peptides produced a rapid and transient rise in Ins(1,4,5)P3 (max. 5-15 s), followed by a slow sustained rise. Ins(1,4,5)P3 was metabolized by both dephosphorylation and phosphorylation pathways, but the relative importance of the two metabolic pathways was different under stimulation by each of the three peptides. These findings show that adrenal glomerulosa cells can distinguish between the stimulation of phosphatidylinositol turnover by three different effectors. These differences in the pathway may be associated with the observed different steroidogenic and Ca2+ responses to the three peptides.

Abscisic acid resistant mutants in the fern Ceratopteris: characterization and genetic analysis

1985 ◽  
Vol 63 (9) ◽  
pp. 1582-1585 ◽  
Author(s):  
Leslie G. Hickok
Keyword(s):  
Abscisic Acid ◽  
Genetic Analysis ◽  
Sexual Differentiation ◽  
Double Mutant ◽  
Acid Resistance ◽  
The Other ◽  
Additive Effects ◽  
Wild Type ◽  
Resistant Mutants ◽  
Moderate Resistance

Abscisic acid normally inhibits growth and male sexual differentiation (antheridia formation) in gametophytes of the fern Ceratopteris. Abscisic acid resistant mutants show increased growth and sexual differentiation in comparison with the wild type when cultured in the presence of abscisic acid. Two different mutants that confer resistance to the effects of abscisic acid have been fully characterized. One shows moderate resistance and the other strong resistance. The mutations involve separate but linked loci. Recombination between the loci yields double mutant (cis) recombinants that exhibit additive effects and show exceptional levels of abscisic acid resistance.

Hybrids between Schistosoma mansoni and S. rodhaini: characterization by cercarial emergence rhythms

Parasitology ◽  
1989 ◽  
Vol 99 (2) ◽  
pp. 225-228 ◽  
Author(s):  
A. Thèron
Keyword(s):  
Schistosoma Mansoni ◽  
Parental Species ◽  
Genetic Determinism ◽  
The Other ◽  
Relative Importance ◽  
Emergence Rhythm ◽  
Cercarial Emergence

SummaryHybridization between Schistosoma mansoni, with a diurnal cercarial emergence rhythm and S. rodhaini, with a nocturnal cercarial shedding pattern leads to F1 and F2 generations, hybrid schistosomes whose chronobiological phenotype of cercariae is characterized by two unequal emergence peaks, one diurnal and the other nocturnal. The relative importance of diurnal and nocturnal peaks depends upon which S. mansoni strain (early or late) is used for the hybridization with S. rodhaini. The results are compared and discussed with those resulting from crosses between intraspecific sympatric and allopatric chronobiological variants (early and late) of S. mansoni. The genetic determinism of the cercarial emergence of schistosomes and the significant differences observed between cercarial shedding patterns of parental species and their hybrids allow the use of this behavioural marker in biological and genetical studies in schistosome populations.

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