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At least 1,747 records · Page 97Linked to original sources
PubMed2004

QTL mapping of chromosomal regions conferring reproductive frost tolerance in barley ( Hordeum vulgare L.).

Spring radiation frost is a major abiotic stress in southern Australia, reducing yield potential and grain quality of barley by damaging sensitive reproductive organs in the latter stages of development. Field-based screening methods were developed, and genetic variation for reproductive frost tolerance was identified. Mapping populations that were segregating for reproductive frost tolerance were screened and significant QTL identified. QTL on chromosome 2HL were identified for frost-induced floret sterility in two different populations at the same genomic location. This QTL was not associated with previously reported developmental or stress-response loci. QTL on chromosome 5HL were identified for frost-induced floret sterility and frost-induced grain damage in all three of the populations studied. The locations of QTL were coincident with previously reported vegetative frost tolerance loci close to the vrn- H1 locus. This locus on chromosome 5HL has now been associated with response to cold stress at both vegetative and reproductive developmental stages in barley. This study will allow reproductive frost tolerance to be seriously pursued as a breeding objective by facilitating a change from difficult phenotypic selection to high-throughput genotypic selection.

Acclimatization↗
PubMed2006

Genetic and environmental origins of obesity relevant to reproduction.

Obesity has a negative impact on reproductive health, particularly in women with polycystic ovarian syndrome (PCOS). Obesity itself is the product of both genetic and environmental influences, although the current 'epidemic' of obesity is largely related to changes in diet and lifestyle. Single gene defects leading to obesity and disordered reproductive function are rare but can are informative about metabolic pathways involved in appetite regulation. There is good evidence that PCOS has an important genetic background, which probably involves the interaction of several genes. The phenotype of PCOS and its impact on reproductive function is profoundly affected by obesity, which, in turn has both genetic and environmental influences. Understanding the genetic basis of PCOS is important but improvements in diet and lifestyle are the best means of improving reproductive function.

Chromosomes, Human, Pair 19↗
PubMed2004

Reproductive ecology of the endangered Alpine species Eryngium alpinum L. (Apiaceae): phenology, gene dispersal and reproductive success.

BACKGROUND AND AIMS: Eryngium alpinum (Apiaceae) is an endangered perennial, characteristic of the Alpine flora. Because the breeding system influences both demographic (reproductive success) and genetic (inbreeding depression, evolutionary potential) parameters that are crucial for population maintenance, the reproductive ecology of E. alpinum was investigated. Specifically, the aims of the study were (1) to determine the factors (resources and/or pollen) limiting plant fitness; and (2) to assess the potential for gene flow within a plant, within a patch of plants, and across a whole valley where the species is abundant. METHODS: Field experiments were performed at two sites in the Fournel valley, France, over three consecutive years. Studies included a phenological survey, observations of pollinators (visitation rates and flight distances), dispersal of a fluorescent powder used as a pollen analogue, the use of seed traps, determination of the pollen/ovule ratio, and an experiment to test whether seed production is limited by pollen and/or by resources. KEY RESULTS: E. alpinum is pollinated by generalist pollinators, visitation rates are very high and seed set is resource- rather than pollen-limited. The short flights of honeybees indicate a high potential for geitonogamy, and low pollen and seed dispersals suggest strong genetic structure over short distances. These results are interpreted in the light of previous molecular markers studies, which, in contrast, showed complete outcrossing and high genetic homogeneity. CONCLUSION: S. The study highlights the usefulness of adopting several complementary approaches to understanding the dynamic processes at work in natural populations, and the conservation implications for E. alpinum are emphasized. Although the studied populations do not seem threatened in the near future, long-term monitoring appears necessary to assess the impact of habitat fragmentation. Moreover, this study provides useful baseline data for future investigations in smaller and more isolated populations.

Ecology↗
PubMed1999

On the origin of species by sympatric speciation.

Understanding speciation is a fundamental biological problem. It is believed that many species originated through allopatric divergence, where new species arise from geographically isolated populations of the same ancestral species. In contrast, the possibility of sympatric speciation (in which new species arise without geographical isolation) has often been dismissed, partly because of theoretical difficulties. Most previous models analysing sympatric speciation concentrated on particular aspects of the problem while neglecting others. Here we present a model that integrates a novel combination of different features and show that sympatric speciation is a likely outcome of competition for resources. We use multilocus genetics to describe sexual reproduction in an individual-based model, and we consider the evolution of assortative mating (where individuals mate preferentially with like individuals) depending either on an ecological character affecting resource use or on a selectively neutral marker trait. In both cases, evolution of assortative mating often leads to reproductive isolation between ecologically diverging subpopulations. When assortative mating depends on a marker trait, and is therefore not directly linked to resource competition, speciation occurs when genetic drift breaks the linkage equilibrium between the marker and the ecological trait. Our theory conforms well with mounting empirical evidence for the sympatric origin of many species.

Animals↗
PubMed1997

The human oocyte. Genetic aspects.

Since the beginning of in vitro fertilization (IVF), basic research has enlightened the field of human reproduction, especially in genetics. Indeed, the contribution of chromosomal anomalies to oocyte disorders and impaired developmental capacities of the embryos is now well known. Among oocytes that failed to fertilize after in vitro insemination, 26.5% were found to be abnormal comprising 13.3% hypohaploidy, 8.1% hyperhaploidy, 1.6% structural anomalies and 3.5% diploidy. The total incidence of abnormalities seems to be correlated to the female status, and was found to be higher in oocytes from women with tubal or unexplained infertility than in those from women whose husband was infertile as a sole cause of couple infertility. Although few oocytes recovered during a natural cycle were studied, gonadotropins widely used to stimulate follicle growth and ovulation do not increase the risk of anomalies. The effect of maternal age on fetal aneuploidy, well documented at birth, has not yet be found unambiguously to be a consequence of an increased rate of aneuploid oocytes. Intra- and extrafollicular influences (perifollicular microvasculature, oxygenation, the presence of residues from cigarette smoke) are able to disturb maturation leading to immaturity and aneuploidy. To conclude, oocyte meiosis is very sensitive to endogenous or exogenous factors, which could lead to chromosomally abnormal oocytes and as a consequence, to abnormal zygotes.

Adult↗
PubMed1989

[Evaluation of genetic risk of radiation during roentgenologic examination of women of reproductive age].

On the strength of the literary data an evaluation of genetic exposure-associated risk during roentgenologic examination of women of the reproductive age is presented. It is demonstrated that the degree of genetic risk depends on women's age at the moment of the roentgenologic examination and the amount of the gonadal dose. Identification of the high-risk exposed populations has been substantiated.

Abnormalities, Radiation-Induced↗
PubMedDate not supplied

Ethical offspring?

Explore the source record for details and available documents.

Child↗
PubMed1994

More fuss about genetics and embryos.

General alarm about genetics continues, fanned by the expectation that what may one day be possible will be a reality tomorrow. Moderation is the most urgent need, but understanding would also help.

Aborted Fetus↗
PubMed2002

On a genetic assessment of the adaptedness of forest reproductive material.

Assessment of the adaptedness of forest tree populations and the reproductive material derived from them is largely based on historical records and observations on extant distributions of phenotypic traits. Genetic criteria are, if at all, usually considered only in the form of heuristic reasoning. A main reason for this situation lies in the lack of operational concepts that clearly distinguish between viability selection and adaptation. The present paper makes an attempt towards this aim by showing that the adaptational optimization of viability selection processes rests on three constituent features which allow minimization of the implied overall mortality at each relevant selection stage and across all of these stages. Indices are developed that measure the degree of adaptational optimization of viability selection. The concept and its indices are applied to an analysis of isozyme data obtained for an approved beech seed stand and reproductive material derived from this stand. An approved seed stand is required to be adapted, and this property is expected to be preserved in the derived reproductive material. Our observations revealed substantial degrees of overall reductions and suboptimal selection during the production process. Suboptimality is unevenly distributed over the stages of the production process, and stages of strongest suboptimality vary among gene loci. A preliminary explanation is given for a conspicuous effect on selective optimality that is consistently observable at the stage of seedling development across all loci.

Journal Article↗
PubMed2001

Chromosomal inversions and the reproductive isolation of species.

Recent genetic studies have suggested that many genes contribute to differences between closely related species that prevent gene exchange, particularly hybrid male sterility and female species preferences. We have examined the genetic basis of hybrid sterility and female species preferences in Drosophila pseudoobscura and Drosophila persimilis, two occasionally hybridizing North American species. Contrary to findings in other species groups, very few regions of the genome were associated with these characters, and these regions are associated also with fixed arrangement differences (inversions) between these species. From our results, we propose a preliminary genic model whereby inversions may contribute to the speciation process, thereby explaining the abundance of arrangement differences between closely related species that co-occur geographically. We suggest that inversions create linkage groups that cause sterility to persist between hybridizing taxa. The maintenance of this sterility allows the species to persist in the face of gene flow longer than without such inversions, and natural selection will have a greater opportunity to decrease the frequency of interspecies matings.

Animals↗
PubMed1995

Male gamete output of asexuals and the dynamics of populations polymorphic for reproductive mode.

Most asexual plants retain male sexual function, albeit at levels much lower than their sexual counterparts. This phenomenon has not typically received full representation in mathematical models of the cost of sex. We formulate and analyze a genetic model of reproductive mode in order to study the evolutionary dynamics of populations consisting of both sexual and asexual individuals. Our model incorporates levels of production and fertility of male gametes produced by individuals that are asexual in their female function, that vary from zero to a level equal to that in a sexual individual. This encompasses a range of naturally occurring situations that has been beyond the scope of most previous theoretical studies. We show that the cost of sex is frequency-dependent in many biologically relevant situations. Consequently, the fitness advantage needed for sexuals to resist invasion by asexuals may frequently be much less than twofold. However, the fitness advantage required for sexuals successfully to invade an asexual population may be much higher. Moreover, the viability/fertility advantage required by sexuals to equal the fitness of asexuals is not necessarily equal to the intrinsic cost of sex, but may be greater when asexual individuals produce fertile male gametes. We also show that panmictic populations cannot be stably polymorphic for reproductive mode when fitnesses are constant, and that the conditions for the fixation of sexual or asexual genotypes are not affected by the degree of dominance at the locus determining reproductive mode. With frequency-dependence, and no possibility of stable polymorphism, the reproductive mode that finally evolves will, in many cases, depend upon the initial frequencies of asexual and sexual individuals.

Biological Evolution↗
PubMed2003

New microinsemination techniques for laboratory animals.

Since the development of a reliable mouse intracytoplasmic sperm injection (ICSI) technique in 1995, microinsemination techniques have been widely applied in several laboratory species. As gametes and embryos have specific biological and biochemical features according to the species, technical improvements are necessary for successful microinsemination that subsequently leads to normal fetal development in several species. Recent advanced reproductive research involving genetic engineering often depends on microinsemination techniques that require a high degree of skill, and new human assisted reproductive technology (ART) requires experimental models using laboratory animals. The accumulation of technical improvements in these fields should accelerate the development of microinsemination techniques in mammals, including humans.

Animals↗
PubMed2005

Genetic variation and geographic distribution of porcine reproductive and respiratory syndrome virus in Japan.

Porcine reproductive and respiratory syndrome virus (PRRSV) has two genotypes, the North American-type (NA-type) and the European-type (EU-type), and each genotype is also genetically diverged. We sequenced the ORF5 gene of 30 PRRSVs isolated from 23 prefectures of Japan during 1992 and 1993 and during 2000 and 2001. All of the isolates were of the NA-type. Phylogenetic analysis of the overall NA-type viruses isolated from around the world identified five major genetic clusters. The 1992-1993 Japanese samples belonged to only two genetic clusters, while the 2000-2001 samples included more diverged ORF5 genomes. One genetic cluster, which included 63% (20/32) of Japanese isolates, one Taiwanese isolate and one Chinese isolate, was mainly found in the eastern part of Japan. Another genetic cluster, which was found in various areas around the world, was distributed in the western part of Japan.

Animals↗
PubMed2001

Spatial patterns of genetic diversity in Posidonia oceanica, an endemic Mediterranean seagrass.

Posidonia oceanica is an endemic seagrass species in the Mediterranean Sea. In order to assess levels of genetic structure in this species, the microsatellite polymorphism was analysed from meadows collected in several localities, along the coasts of the Tyrrhenian Sea (Mediterranean Sea). The existence of single population units and the recruitment of seedlings collected in some localities were investigated. Moreover, genetic structure at different spatial scales and biogeographic relationships among populations were also assessed. Our analysis showed the existence of clear patterns of genetic structure in P. oceanica in the area considered in the analysis. P. oceanica, in fact, is present in separate meadows that represent discrete populations, characterized by low genetic diversity. Comparable levels of genetic variability between mature meadows and seedlings were found. Patterns of genetic relatedness among populations seem to be in accord with direction of dominant current flux in the whole area, separating South Tyrrhenian from North Tyrrhenian populations. Moderate levels of gene flow between populations and genetic substructure within populations, together with the finding of the limited role of sexual reproduction in increasing genetic variability, should be a cause for concern for the persistence of this essential resource in the Mediterranean basin.

Genetic Variation↗
PubMed2005

Genetic analysis for drought resistance of rice at reproductive stage in field with different types of soil.

Drought resistance of rice is a complex trait and is mainly determined by mechanisms of drought avoidance and drought tolerance. The present study was conducted to characterize the genetic basis of drought resistance at reproductive stage in field by analyzing the QTLs for drought response index (DRI, normalized by potential yield and flowering time), relative yield, relative spikelet fertility, and four traits of plant water status and their relationships with root traits using a recombinant inbred population derived from a cross between an indica rice and upland rice. A total of 39 QTLs for these traits were detected with individual QTL explained 5.1-32.1% of phenotypic variation. Only two QTLs for plant water status were commonly detected in two environments, suggesting different mechanisms might exist in two types of soil conditions. DRI has no correlation with potential yield and flowering time under control, suggesting that it can be used as a good drought resistance index in field conditions. The co-location of QTLs for canopy temperature and delaying in flowering time suggested a usefulness of these two traits as indexes in drought resistance screening. Correlation and QTL congruence between root traits and putative drought tolerance traits revealed that drought avoidance (via thick and deep root traits) was the main genetic basis of drought resistance in sandy soil condition, while drought tolerance may play more role in the genetic basis of drought resistance in paddy soil condition. Therefore, both drought mechanisms and soil textures must be considered in the improvement of drought resistance at reproductive stage in rice.

Adaptation, Physiological↗
PubMed1996

The genetics of male infertility.

PURPOSE: We provide an up-to-date summary of the genetic aspects of male infertility. MATERIALS AND METHODS: The literature on male infertility was extensively reviewed. RESULTS: Genetic defects are associated with a variety of clinical presentations by the infertile man ranging from gonadotropin-releasing hormone deficiency to spermatogenic failure to obstructive azoospermia. Microsurgery and micromanipulation of gametes make it possible for many of these men to father children. However, with each successive breakthrough in treatment of male infertility there is an increased risk of transmitting genetic abnormalities to the progeny. CONCLUSIONS: Transmission of genetic defects through assisted reproductive techniques can have serious long-term implications. Assisted reproductive techniques should not be initiated in men with a possible or known genetic cause of infertility without prior genetic counseling and risk assessment. Clinicians and researchers involved in reproductive medicine must recognize that, although these techniques have revolutionalized the treatment of male infertility, they have the risk of passing genetic abnormalities to the progeny. Therefore, researchers must proceed cautiously with development and application of assisted reproductive technologies to avoid creating future generations of genetically abnormal individuals. The first step in accomplishing this goal is through an increased understanding of the genetic basis of male reproductive failure.

Chromosome Aberrations↗
PubMed2001

Genetic (co)variances for calving difficulty score in composite and parental populations of beef cattle: II. Reproductive, skeletal, and carcass traits.

There is limited genetic information relating calving difficulty and body weights to other productive and reproductive traits. Such information is useful for specifying selection criteria and for predicting economic consequences of selection. Genetic, maternal, and environmental covariances of six productive and reproductive measurements with calving difficulty, birth weight, 200-d weight, and 168-d postweaning gain were estimated in 12 experimental populations of cattle. Calf (direct) genetic effects resulting in longer gestation length were associated with increased calving difficulty and birth weight. Maternal genetic effects of increased gestation length and heavier birth weight were significantly associated. Lighter birth weight and reduced calving difficulty were associated with earlier heifer age at puberty. Increases in direct genetic effects of calving difficulty, 200-d weight, and postweaning gain were associated with a small increase in direct effect of scrotal circumference. Increased direct genetic effects of scrotal circumference were correlated with maternal effects decreasing calving difficulty and increasing 200-d weight. Direct effects of the skeletal measurements, yearling hip height, and heifer pelvic area were positively correlated with direct effects of calving difficulty, birth weight, 200-d weight, and postweaning gain, positively correlated with maternal effects for birth weight and 200-d weight, and negatively correlated with maternal calving difficulty. Percentage of retail product was positively associated with calving difficulty and negatively associated with 168-d gain. Predicted genetic change in calving difficulty resulting from one standard deviation of selection for either calving difficulty score or birth weight was much larger than for any other traits. Selection for 200-d weight, 168-d postweaning gain, hip height, pelvic area, or scrotal circumference was predicted to have opposite effects on direct and maternal calving difficulty. Estimated genetic correlations indicate some small to moderate relationships between calving difficulty and the measured productive and reproductive traits. However, selection for reduced calving difficulty should be based on calving difficulty score and(or) birth weight because of their superiority in predicted genetic change.

Animals↗
PubMed1984

Impact of genetic manipulation.

Genetic progress for production in dairy cattle is 50% or less of optimum. Manipulation of the reproductive process to increase genetic gains was reviewed. Economics of manipulating the reproductive process was evaluated by equating future discounted net income to current discounted expenses and solving for the break-even cost of the technique for 1 to n years the technique is employed. Techniques such as embryo transfer and sexed semen can be evaluated for economics. A system of splitting female embryos to produce performance-tested female genotypes was presented. The system has the capability of increasing genetic gains per year by 35%. The proposed system could be profitable if it is incorporated in the artificial insemination system and directed by professional geneticists.

Animals↗