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At least 1,369 records · Page 76Linked to original sources
PubMed2001

Genetic associations under mixed mating systems: the Bennett-Binet effect.

Using elementary algebraic geometry and computational commutative algebra, supported by the program Macaulay2, we studied and developed operators that define the zygotic and gametic evolution under a mixed-mating system with parameters s selfing rate, r recombination rate, and g relative fitness of inbreeders, for any possible combination of initial zygotic or gametic frequencies with two alleles at each of two loci. We found that (i) the allelic frequencies are preserved in every generation; (ii) the gametic frequencies converge to values that depend exclusively on the allelic frequencies; (iii) every zygotic population converges to a population in equilibrium with double heterozygotes equally frequent; (iv) the rate of convergence decreases to arbitrary small values with sufficiently small values of r or with sufficiently large values of s and (v) as g decreases, the maximal 'association between the two loci' occurs with higher values of selfing. We also found generalizations for the case of several alleles at each locus.

Alleles↗
PubMed2002

Technical procedure and ethical behaviour in biotechnologies of reproduction.

BACKGROUND: The significant and constant progress of biotechnologies applied to sterility and infertility has induced a deeper reflection about bioethical problems. The analysis of only the biological dimension, about the results achieved and desirable future prospects, decreases, leaving out the anthropological dimension. It is therefore necessary to make reference to both the limits of the basic or applied research and to the usual welfare procedure. The aim, that the article sets itself, is to proceed to the bioethical analysis of the most significant topics of artificial insemination and assisted procreation; and it submits to anthropological evaluation the technical aspects, which characterize both the procreation techniques and the research prospects in this area. METHODS: The bioethical analysis, used as a method of study and research, has availed itself of structured reasoning through the evaluation of the scientific, anthropological and legal-deontological dimensions, from an interdisciplinary point of view. The definition of the ethical norm, supported by authors, has been inferred from the analysis of the above-mentioned dimensions, considering the already known bioethical models. In particular, the authors analyse these topics through the model of ontologically based personalism, which suggests, and highlights, ethical norms, both as regards the basic and applied research and as regards usual welfare procedure, in opposition to models like moral sociologism, biologism, moral evolutionism and contractualism. From the beginning we defined "technical procedure" and "ethical behaviour", highlighting the interaction between them. We have made a distinction between artificial insemination, as a substitutive technique, and assisted procreation, as a facilitative technique. In addition through biological and anthropological results we have evaluated the embryo both ontologically and biologically. So we have defined "ontological and biological embryo status". RESULTS AND CONCLUSIONS: The evaluation of the proposed topics for assisted procreation and against artificial insemination, the interaction between technical procedure and ethical behaviour, the acknowledgement of the embryo and personal dignity in every procedure are the principal results and the conclusions that we have arrived at, as regards the bioethical model of ontologically based personalism.

Biotechnology↗
PubMed2002

Mutation and premating isolation.

While premating isolation might be traceable to different genetic mechanisms in different species, evidence supports the idea that as few as one or two genes may often be sufficient to initiate isolation. Thus, new mutation can theoretically play a key role in the process. But it has long been thought that a new isolation mutation would fail, because there would be no other individuals for the isolation-mutation-carrier to mate with. We now realize that premeiotic mutations are very common and will yield a cluster of progeny carrying the same new mutant allele. In this paper, we discuss the evidence for genetically simple premating isolation barriers and the role that clusters of an isolation mutation may play in initiating allopatric, and even sympatric, species divisions.

Animals↗
PubMed2002

[Study of molecular genetics of the size of reproductive organs and litter size in the sow].

The mutations of ESR, PRLR and FSHR genes were investigated by SNP; 103 F2 sows were slaughtered and their reproductive organs were determined; the litter size of sow was recorded. The linkage between mutations of genes and size of reproductive organ, litter size was analyzed. The results revealed: these sows that could provide more piglets with bigger reproductive organs usually carried genotype like as genotype BB on the sites of ESR, FSHRB and the genotype AA on the sites of ESRB and PRLR, that is, the genotype of BB on the sites of ESR or FSHRB in sow was not only helpful to promote growth of reproductive organs, but also benefit to improve litter size; The size of productive organs and litter size of the sow with genotype AA on the sites of ESRB or PRLR were significantly higher than those of sow with genotype AB or BB.

Animals↗
PubMed2003

The work of the Medical Research Council.

The above committee is one of Parliament's select committees that undertake enquiries of considerable depth in their particular fields. Its latest enquiry looked at the MRC in general, and also specifically at how it is handling the Biobank project. Its general findings are scathing of the MRC's performance and mismanagement of its funds, concluding that 'the anger of the research community at MRC's funding problems is not only understandable but entirely justified.' The following are the committee's conclusions and recommendations on Biobank--the collection of blood samples, lifestyle details and medical histories from 500,000 middle-aged Britons, and its general conclusions.

Biological Specimen Banks↗
PubMed2004

The genetics of floral divergence and postzygotic barriers between outcrossing and selfing populations of Arenaria uniflora (Caryophyllaceae).

The genetic architecture of floral traits involved in the evolution of self-pollination provides a window into past processes of mating system divergence. In this study, we use two generations of crosses between highly selfing and predominantly outcrossing populations of Arenaria uniflora (Caryophyllaceae) to determine the minimum number, average dominance relationships, and pleiotropic effects of genetic factors involved in floral divergence. Comparison of the F1 and F2 phenotypic means with the expectations of a completely additive model of gene action revealed a primarily additive genetic basis for floral characters associated with mating system variation. The exception was flower life span, which showed partial dominance of the outcrosser phenology. In contrast to similarly divergent species, the substantial differences in flower size between these A. uniflora populations appear to involve relatively few genes of large effect (minimum number of effective factors = 2.2 +/- 2.8 SE). In addition, correlations among traits in the F2 generation indicate that pleiotropy may be an important feature of the genetic architecture of floral evolution in A. uniflora. The evolution of selfing via major modifiers of floral morphology is consistent with other evidence for ecological selection for preemptive self-pollination in A. uniflora. Analyses of the genetic basis of autonomous selfing were complicated by hybrid breakdown in both F1 and F2 generations. Only F1 hybrids showed reductions in female fertility, but about 30% of F1 and F2 hybrids exhibited partial or complete male sterility. Male sterile flowers were characterized by short stamens, reduced petals, and a lack of protandry, as well as indehiscent anthers. This morphological breakdown mimics environmental disruptions of floral development and may result from novel genic interactions in hybrids.

Analysis of Variance↗