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PubMed1978

Reproduction and breeding of goats.

Reproduction and genetics of the goat are reviewed with a view of increasing their contribution to mankind. The goat contributes most in tropical regions (within 30 degrees of the equator). The most important product from the goat is milk with meat a close second. Other products are minor. Reproductive rate is a problem only with the Angora goat, but increased reproduction with any type of goat would contribute to improved efficiency. Also, a knowledge of the reproductive phenomenon is necessary for effective management. Genetic studies of goats are limited, but this should not limit improvement programs. Excellent genotypes for producing milk and fiber are available, but adaptation to tropical conditions is needed. Even within temperature regions, there is little evidence of progress in breeding for milk production. Little has been done on the development of the goat as a meat animal. Also, research on crossbreeding for milk or meat production is limited.

Abortion, Veterinary↗
PubMed2001

Genetic structure of the saxicole Pitcairnia geyskesii (Bromeliaceae) on inselbergs in French Guiana.

South American inselbergs constitute singular and fragmented habitats in the tropical rain forest. Pitcairnia geyskesii is restricted to these habitats and exhibits both sexual and asexual reproduction. The genetic structure of populations on three inselbergs in French Guiana is examined by analysis of ten isozyme loci. All analyzed populations show high levels of genetic variation. On average, 63.3% of loci per population were polymorphic, with a mean number of 2.21 alleles per polymorphic locus, and mean observed and expected heterozygosities of 0.185 and 0.183, respectively. The analyses of genetic variability displayed at different levels (inselbergs, subpopulations, and mats) give different but complementary information. A significant multilocus disequilibrium was detected in one subpopulation, whereas none was observed within the whole populations sampled on the three inselbergs. Tests on spatial genetic structure indicate a patchy distribution of genotypes on two inselbergs. The data give some insights on the reproductive behavior of P. geyskesii. (1) Efficient sexual reproduction leads to seed recruitment at the level of the inselberg. (2) Both clonality and seed recruitment occur within mats. (3) Vegetative spread by fragmentation is involved in the establishment of new mats. There is substantial differentiation (F(ST) = 0.322) and low gene flow among inselbergs (Nm = 0.234). High genetic diversity within inselbergs appears as a consequence of the association of genet longevity induced by clonal replication and recruitment of new genets produced by sexual reproduction.

Journal Article↗
PubMed1991

Evidence of genetic recombination in Leishmania.

In the genus Leishmania there has been no convincing demonstration of genetic exchange, and it has been proposed that reproduction is clonal. However, preliminary characterization of two strains of Leishmania isolated from wild animals in a zoonotic focus of cutaneous leishmaniasis in the Eastern Province of Saudi Arabia, has suggested that they may represent hybrids of Leishmania major and Leishmania arabica. Evidence presented here strongly supports this hypothesis. Isoenzyme analysis and molecular karyotyping of cloned organisms indicated that the putative hybrids are distinct from other species of Leishmania, and possess characteristics of both L. major and L. arabica. Experiments using highly specific probes demonstrated that kinetoplast minicircle DNA from the putative hybrid contained L. major-specific, but not L. arabica-specific sequences. DNA fingerprinting data obtained using 6 genomic DNA probes were consistent in all cases with a L. major/L. arabica recombinant genotype, and implied both diploidy and allelic segregation. These observations suggest that sexual reproduction may generate genetic diversity within natural Leishmania populations.

Animals↗
PubMed2000

Population structure of Hydropsyche exocellata. Genetic homogeneity in a zone of fragmented distribution.

Using four allozymic loci, we analysed the genetic structure and differentiation of Hydropsyche exocellata (Trichoptera; Hydropsychidae) larvae in seven sites along the Upper Loire River (France). The genetic differentiation is low for this species despite distribution patchiness, and only due to one locus in one study site. No trend relating genetic differentiation to geographic distance (isolation by distance) was observed. Significant deviations from Hardy-Weinberg equilibrium were observed at most sites and loci. The population genetics analysis of an amphibiotic insect such as H. exocellata in light of current ecological and population genetics knowledge is discussed following two main factors: 1) sampling of partially reproductively isolated, genetically distinct subpopulations, and 2) form of selection. Despite knowledge on several aspects of the ecology of H. exocellata in the River Loire, numerous points limit genetic data interpretation. These points are underlined and discussed with reference to studies on other amphibiotic insects.

Animals↗
PubMed2000

Natural selection at work.

Although much is known about the genetic basis of reproductive isolation between species, little is understood about its underlying evolutionary causes. A study of two very closely related, but reproductively isolated, plant species has provided some valuable insights.

Plant Physiological Phenomena↗
PubMedDate not supplied

[Assisted reproduction and artificial insemination and genetic manipulation in the Criminal Code of the Federal District, Mexico].

The article that one presents has for purpose outline and comment on the recent modifications to the Penal Code for the Federal District of México which establish, for the first time, crimes related to the artificial procreation and to the genetic manipulation. Also one refers to the interaction of the new legal texts with the sanitary legislation of the country. Since it will be stated in some cases they present confrontations between the penal and the sanitary reglamentation and some points related to the legality or unlawfulness of a conduct that stayed without the enough development. These lacks will complicate the application of the new rules of the Penal Code of the Federal District.

Genetic Engineering↗
PubMed2006

Variance components for live weight, body measurements and reproductive traits of pair-mated ostrich females.

Estimates of genetic parameters for reproductive traits, live weight and body measurements were obtained using data from a pair-mated ostrich flock at Oudtshoorn in South Africa. Reproductive traits included total egg and chick production, along with hatchability percentage. Live weight, chest circumference and tail circumferences were recorded at the commencement and cessation of breeding. Heritability estimates (h(2)) were 0.23 for egg production, 0.20 for chick production, 0.10 for hatchability, 0.20 to 0.34 for live weight, 0.12 for chest circumference and 0.30 to 0.38 for tail circumference. Female permanent environmental effects (c(2)) amounted to 0.18 for egg production, 0.18 for chick production, 0.21 for hatchability, 0.32 to 0.36 for live weight and 0.23 to 0.32 for chest circumference. Service sire exerted significant effects only on hatchability (0.22) and subsequently chick production (0.09). Genetic correlations of reproductive traits with live weight were low to moderate, variable in sign, and did not differ significantly from zero. Correlations between live weight recorded at the beginning and end of the breeding season were unity for additive genetic and permanent environmental effects. Egg and chick production were highly correlated genetically and phenotypically, with the genetic correlation exceeding the theoretical limit. In unconstrained analyses, hatchability was positively related to chick production, including at the service sire level. Selection gains in the current flock and future generations are likely. No significant adverse relationships were found between live weight, body measurements and reproductive traits.

Animals↗
PubMed2002

Resolving the paradox of sex and recombination.

Sexual reproduction and recombination are ubiquitous. However, a large body of theoretical work has shown that these processes should only evolve under a restricted set of conditions. New studies indicate that this discrepancy might result from the fact that previous models have ignored important complexities that face natural populations, such as genetic drift and the spatial structure of populations.

Animals↗
PubMed1989

Eugenic sterilization: a preliminary comparison of the Scandinavian experience to that of Germany.

The paper argues that historical analysis and explanation of eugenics in Germany can benefit much from systematic comparison to Scandinavia. Common cultural background and quite similar development up to 1933 provides a background for isolating salient causes in Nazi population policies. This comparison will also help a more precise understanding of the mutual dependence between science and politics in the case of eugenics. The author holds that many of the geneticists who participated in the eugenics debates of the 1930's and 1940's had a clearer grasp of the distinction between science and politics than most present day historiographers of eugenics.

Eugenics↗
PubMed2003

Crossing experiments detect genetic incompatibility among populations of Triatoma brasiliensis Neiva, 1911 (Heteroptera, Reduviidae, Triatominae).

Triatoma brasiliensis is composed of at least four geographic populations (brasiliensis, melanica, macromelasoma, and juazeiro) that have distinct chromatic, morphologic, biologic and ecologic patterns, and genetic composition. Reciprocal crosses between all pairwise combinations were carried out in order to evaluate the genetic and reproductive compatibility of these four populations. The F1 individuals developed normally and the resulting adults were crossed again to test the F2 and F3 viability. Genetic incompatibility was found between melanica and brasiliensis populations.

Animals↗
PubMed1992

The potential role of molecular genetic manipulation in the improvement of reproductive performance.

Revolutionary opportunities for the modification of animal performance are being created by the development of new methods for embryo manipulation and the application of molecular biology. This paper reviews the potential application of these procedures for the improvement of reproductive performance in livestock. There are three sections: a consideration of the methods of molecular manipulation that are available at present and those that seem likely to become available, a discussion of the modifications to hormonal systems and, finally, an analysis of candidate genes for manipulation of seasonality, number of ovulations, sex ratio and prenatal survival. The analysis points to a number of ways forward. Many of the most promising opportunities will depend upon the isolation of embryonic stem cells or the establishment of alternative methods of site-directed mutation. In most cases, the genes of interest have not yet been cloned and much remains to be learned about the molecular regulation of reproduction. A greater understanding seems likely to reveal the inadequacies of some of the present suggestions, but it is also certain to reveal further opportunities. However, in the longer term, there seems to be a real prospect of modification of at least some of these aspects of reproductive performance by molecular means.

Animals↗
PubMed1990

Utilisation and control of biotechnological procedures in veterinary science.

The author retraces the history of "biotechnology" and the successive stages of its application in veterinary sciences. An inventory is given of potential applications in animal health (diagnosis, prevention and treatment of diseases), genetics, animal reproduction (direct and indirect contributions) and nutrition (at the levels of fodder plants, fermentation or prefermentation of feed, and animal metabolism). The control of biotechnological procedures is discussed, with reference to categories of risk and ways of averting risk, and control at national and international levels. There is growing interest in the application of biotechnology to animal reproduction and to the diagnosis and treatment of animal diseases, but developing ways to prevent disease is slow because considerable time is needed to evaluate risks.

Animal Diseases↗
PubMed2001

Genetic linkage of ecological specialization and reproductive isolation in pea aphids.

The evolution of ecological specialization generates biological diversity and may lead to speciation. Genetic architecture can either speed or retard this process. If resource use and mate choice have a common genetic basis through pleiotropy or close linkage, the resulting genetic correlations can promote the joint evolution of specialization and reproductive isolation, facilitating speciation. Here we present a model of the role of genetic correlations in specialization and speciation, and test it by analysing the genetic architecture of key traits in two highly specialized host races of the pea aphid (Acyrthosiphon pisum pisum; Hemiptera : Aphididae). We found several complexes of pleiotropic or closely linked quantitative trait loci (QTL) that affect key traits in ways that would promote speciation: QTL with antagonistic effects on performance on the two hosts are linked to QTL that produce asortative mating (through habitat choice). This type of genetic architecture may be common in taxa that have speciated under divergent natural selection.

Adaptation, Biological↗
PubMed2002

[Genetic analysis on diversity of reproductive modes of silver crucian carp inferred by transferrin and isozyme markers].

Silver crucian carp (Carassius auratus gibelio) has been known for its gynogenetic reproduction. In this paper, eggs from clone F of gynogenetic silver crucian carp were inseminated respectively by sperms of clone D, clone A and common carp, and polymorphic patterns of transferrin and isozymes of the produced three offspring FD, FA and FL were studied comparatively to explore the diversity in reproductive modes of silver crucian carp. As control, zymograms of FL progenies exhibited a maternally clonal inheritance, and gynogenesis was reconfirmed. However, differentiation of morphs and electrophoretic patterns was both observed among the FD progenies, and detection of bands specific for the clone F or clone D in some FD individuals urged the occurrence of recombination. Furthermore, extreme linkage disequilibrium for different protein loci suggested that linkage groups composed of different genes might function as the fundamental unit in the recombination. With respect to FA group, phenotypes of parental clones were both detected in the F2 generation (FA x FA progenies) while only maternal phenotypes were detected in the F1 generation. It appeared that both the parental chromosome sets could be transmitted to the offspring but expression of paternal genes were fundamentally upset in the F1 generation because of incompatibility of the parental genes. Generally, genetic analysis of FD and FA offspring primarily exhibited a particular syngamy for silver crucian carp. Besides the clonal reproduction of gynogenesis, syngamy could provide opportunities of recombination for silver crucian carp, which might remove some genetic loads from the genome and introduce new genotypes. Diversity in reproductive modes might play an important role in ecological adaptation of silver crucian carp.

Animals↗