Genetic Connectedness Research Articles

Genotype by Environment Interaction in Nordic Dairy Cattle Studied Using Reaction Norms

Genotype by environment interaction for production and fertility was studied by use of a reaction norm model. Milk recording data, comprising 927 929 records, were analysed to predict reaction norms for young bulls of the Nordic Red dairy breeds. Random regressions were estimated for each bull, regressing phenotypic values of daughters on herd environment. The phenotypic measures were 305 days kg protein production and days open in first lactation. The herd environment was defined as the herd-year average of protein production and days open, respectively. Heritability of protein production and days open and genetic correlation between the two traits were estimated as functions of the herd environment. The results showed that the genetic parameters change over environments, which are measured on a continuous scale across countries. Grouping of observations is avoided and thereby the problem of genetic connectedness between groups or countries may be avoided. Although significant genetic variation for the slope of the reaction norm was found, there was little reranking of sires, except between extreme environments. More appropriate models and methods need to be developed for further studies of genetic variation in reaction norms.

Simulation analysis to test the influence of model adequacy and data structure on the estimation of genetic parameters for traits with direct and maternal effects.

Simulations were used to study the influence of model adequacy and data structure on the estimation of genetic parameters for traits governed by direct and maternal effects. To test model adequacy, several data sets were simulated according to different underlying genetic assumptions and analysed by comparing the correct and incorrect models. Results showed that omission of one of the random effects leads to an incorrect decomposition of the other components. If maternal genetic effects exist but are neglected, direct heritability is overestimated, and sometimes more than double. The bias depends on the value of the genetic correlation between direct and maternal effects. To study the influence of data structure on the estimation of genetic parameters, several populations were simulated, with different degrees of known paternity and different levels of genetic connectedness between flocks. Results showed that the lack of connectedness affects estimates when flocks have different genetic means because no distinction can be made between genetic and environmental differences between flocks. In this case, direct and maternal heritabilities are under-estimated, whereas maternal environmental effects are overestimated. The insufficiency of pedigree leads to biased estimates of genetic parameters.

Simulation analysis to test the influence of model adequacy and data structure on the estimation of genetic parameters for traits with direct and maternal effects

Simulations were used to study the influence of model adequacy and data structure on the estimation of genetic parameters for traits governed by direct and maternal effects. To test model adequacy, several data sets were simulated according to different underlying genetic assumptions and analysed by comparing the correct and incorrect models. Results showed that omission of one of the random effects leads to an incorrect decomposition of the other components. If maternal genetic effects exist but are neglected, direct heritability is overestimated, and sometimes more than double. The bias depends on the value of the genetic correlation between direct and maternal effects. To study the influence of data structure on the estimation of genetic parameters, several populations were simulated, with different degrees of known paternity and different levels of genetic connectedness between flocks. Results showed that the lack of connectedness affects estimates when flocks have different genetic means because no distinction can be made between genetic and environmental differences between flocks. In this case, direct and maternal heritabilities are under-estimated, whereas maternal environmental effects are overestimated. The insufficiency of pedigree leads to biased estimates of genetic parameters.

Selection on purebred and crossbred Performance for litter size in pigs*

Abstract. The present study deals with estimation of genetic parameter for purebred and crossbred Performance of live born piglets, in order to choose the optimal selection method. Data sets of two pure breeds, line L03 and L04, with 5,422 sows, a two line crossbred, L303, with 3,553 sows and a three line crossbred, L350, with 3,609 sows of a North-German breeding Company were recorded. Estimated genetic correlation between purebred and crossbred Performance were rg = 0.59 and 0.40 for reciprocal crosses L03xL04 and L04xL03, respectively. Further investigations showed that the genetic correlation is influenced by genotype-environment interactions between a nucleus farm and a farm on production level. Full-sib effects showed a proportion of FS = 0.06 on the phenotypic variance of litter size. They were confounded with additive genetic variance and permanent environment variance, when full-sib effects were neglected. The percentage of equal selected purebred sires of line L03 were 80% when 30% of the sires selected on purebred or crossbred breeding values. Accuracy of estimated breeding values of purebred sires increased when crossbred Information were considered additionally from 0.32 to 0.38 for line L03 and 0.46 to 0.47 for line L04. Genetic correlation between purebred and crossbred Performance, the genetic connectedness between nucleus and production and the presence of genotype-environment interactions were analysed to have high influence on the value of additionally considered crossbred Performance.

"Det føles ikke-mandigt på en måde"

The article addresses the theme of "masculinities" from the perspective of infertile men and their partners. It argues that experiences of infertility should be understood as disruption in relation to the body and in relation to the narrative of life that is informed by cultural notions of kinship and gender. These notions are closely connected to a culturally specific story of coming-into-being, which gives symbolic priority to biological procreation and genetic connectedness. Being a real father and a real man depends on procreative abilities. In order to come to terms with infertility, infertile men try to redefine such ideologies of authenticity. The article illustrates how infertile men are confronted by strong cultural associations between fertility, sexuality and masculinity, and how these notions are related to other ideas of masculinity such as independence of the individual, ability to be a provider and a conception of the "intact" body. Finally, the article demonstrates how men and women differ in coping with infertility, childlessness and fertility treatment, and their longings for parenthood. However, gender is not the only difference, which makes a difference in the world of infertile and childless people. The ideas of masculinities unfold through men's relations with other men and through generational differences and similarities.

THE INFLUENCE OF POPULATION SIZE AND ISOLATION ON GENE FLOW BY POLLEN IN SILENE ALBA.

In a series of experiments conducted over two seasons, we used arrays of experimental populations to examine the effects of flower number and distance between patches on gene flow by pollen. For this study we used the dioecious, short-lived perennial plant Silene alba (Caryophyllaceae). This species lives in disturbed roadside and agricultural habitats and displays a weedy population dynamic with high colonization and extinction rates. The motivation for the study was to understand what factors may be influencing genetic connectedness among newly colonized populations within a regional metapopulation. By using experimental populations composed of genotypes homozygous at a diagnostic locus, it was possible to identify explicitly pollen movement into a focal patch as a function of flower number and distance to the nearest neighboring patch. Overall, the mean immigration rate (measured as the fraction of seeds sired by males outside the focal patch) at 20 m was just over 47%, whereas at 80 m immigration rates were less than 6%. In addition, by knowing the context in which each of these gene-flow events occurred, it was possible to understand some of the factors that influenced the exchange of genes. Both the number of flowers in the focal population (target) and in the neighboring populations (source) had a significant effect on the frequency of gene flow. Our experimental data also demonstrate that factors that influence gene flow at one spatial scale may not act in the same way at another. Specifically, the influence of target size and the relative size of the target and source patches on rates of gene flow depended on whether the patches were separated by 20 m or 80 m. These data suggest that the patterns of gene flow within a metapopulation system can be complex and may vary within a growing season.

Lay and professional knowledge of genetics and inheritance

Despite almost a century of educational effort, studies of both schoolchildren and adults show that the public understanding of Mendelian genetics is very limited. A similar conclusion is drawn from studies of those who have been offered explanations of inheritance in genetic counselling clinics. The aim of this paper is to provide an explanation of these observations. It is argued that Mendelian explanations of inheritance conflict in a number of ways with a lay knowledge of inheritance that is general in society. Furthermore, it is suggested that lay knowledge is grounded in concepts of kinship which are themselves sustained by everyday social practice and relationships, which may make the lay knowledge of inheritance particularly resistant to change. It is suggested that Mendelian explanations may not be easily assimilated because of the conflicts with pre-existing lay knowledge that an individual holds. Preliminary results are described from an empirical study which tests the hypothesis that ideas of genetic connectedness are derived from concepts of kin relationships. The evidence appears to confirm the hypothesis. Parallels are drawn between the history of the acceptance of Mendel's ideas in the scientific community and the assimilation (or the lack of it) of Mendelian explanations by the public. The paper concludes with a brief discussion of public education in Mendelian genetics in schools and genetic counselling clinics, and the ways in which it could be more effective.

Considerations on genetic connectedness between management units under an animal model.

Connectedness among management units (e.g., herds or regions) is of concern in genetic evaluation. When genetic evaluation is under an animal model, connections occur through A, the numerator relationship matrix. It is argued that the most appropriate measure of connectedness is the average prediction error variance (PEV) of differences in EBV between animals in different management units. It is shown that PEV of differences is influenced by average genetic relationship between and within management units, which in turn affects the variances of estimates of differences between management unit effects. When PEV of differences cannot be computed, use of one of three alternative measures is proposed; the gene-flow method that measures the exchange of genes between management units, measurement of genetic drift variance based on average relationships between and within management units, and measurement of the variance of estimated differences between management units effects. These were correlated with PEV of differences in a test simulation. The gene-flow method, which is simplest to compute, had the lowest correlation (.671). The drift variance and variance of management unit effects methods were highly correlated with PEV of differences (.924 and .995, respectively).

Effects of contrasting patterns of larval dispersal on the genetic connectedness of local populations of two mtertidai starfish, Patiriella calcar and P. exigua

Effects of contrasting patterns of larval dispersal on the genetic connectedness of local populations of two mtertidai starfish, Patiriella calcar and P. exigua

Computing connectedness among management groups under an animal model

In any genetic evaluation procedure connectedness among animals in different management groups (herds) is important in order to account for genetic differences among management groups. Kennedy and Trus (1991) mentioned that under an animal model (IAM), connections occur through the relationship matrix (A). They showed that connectedness can be measured in terms of the proportionate contribution of genes from one herd to the other. This is achieved by computing X1ZTQ, where X and Z are matrices that assign records to herds and animals respectively, Q a matrix that assigns ancestors of animals with records to a single genetic group and T is a lower triangular matrix derived from A, such that A = TDT1, with D a diagonal matrix. In practice the calculation of T may not be feasible with large number of animals because of memory requirements.

Population structure in the coral Pavona cactus: clonal genotypes show little phenotypic plasticity

Electrophoretic data were used to examine the relationship between genotype and growth form, and to assess the contribution of asexual reproduction to recruitment within six local populations of the agaricid coral Pavona cactus from the central and northern Great Barrier Reef. The data revealed the presence of highly replicated clonal genotypes in the five densest populations. In three cases, samples of 50 to 60 colonies collected from 25 m2 areas within the Eclipse Island and Pandora Reef populations each consisted of colonies with only two distinct 4-locus genotypes. More intensive sampling of the population at Eclipse Island showed that colonies with the same 4-locus genotypes were separated by distances of up to 93 m. In contrast, the population at Watson's Bay (Lizard Island) consisted of a few widely scattered and genetically distinct colonies. The samples collected from each population contained a range of growth forms including, in some cases, the entire morphological range described for this species. A strong association of genotype and growth form was detected in samples from all populations, with the exception of Watson's Bay where no such comparison was possible. Nevertheless, some genotypes were represented by more than one growth form and this could reflect the effects of limited phenotypic plasticity. The effects of asexual reproduction reduced the value of these data as a test of the genetic connectedness of the six populations studied. The genetic distance between samples was not simply correlated with geographic distance. This may reflect either the true structure of the breeding population(s) or the effects of asexual reproduction on estimates of allelic frequencies.