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At least 469 records · Page 26Linked to original sources
PubMed2005

Sexual selection can resolve sex-linked sexual antagonism.

Sexual selection is a potent evolutionary force. However, very few models have considered the evolution of female preferences for traits expressed in both sexes. Here we explore how female preferences coevolve with sexually antagonistic traits, which involve alleles that are beneficial to one sex but harmful to the other. We show that with a sexually antagonistic trait on the X chromosome (males XY, females XX), females evolve to prefer mates carrying alleles beneficial to daughters. In contrast, with a Z-linked trait (males ZZ, females ZW), females more often evolve mating preferences for mates carrying alleles beneficial to sons (that is, flashy displays).

Alleles↗
PubMed1979

Counseling for women requesting sterilization: a comprehensive program designed to insure informed consent.

This paper describes the counseling program implemented by a social worker and a family planning counselor for female clinic patients requesting sterilization. Rather than limiting counseling to the guidelines for informed consent established by New York City law, a comprehensive approach is utilized. The program combines the provision of information regarding the procedure and contraceptive alternatives, with an opportunity for individuals to examine the psychosocial components of their request for sterilization. It is the authors' assessment that such comprehensive counseling is essential to provide individuals with the full assistance they need in making the decision to eliminate reproductive capacity, and that legal guidelines should be expanded accordingly.

Adult↗
PubMed2005

The relationship of nucleotide polymorphism, recombination rate and selection in wild tomato species.

We analyzed the effects of mating system and recombination rate on single nucleotide polymorphisms using 14 single-copy nuclear loci from single populations of five species of wild tomatoes (Solanum section Lycopersicon). The taxa investigated comprise two self-compatible (SC) and three self-incompatible (SI) species. The observed reduction in nucleotide diversity in the SC populations compared to the SI populations is much stronger than expected under the neutral effects of the mating system on effective population size. Importantly, outgroup sequences available for 11 of the 14 loci yield strong positive correlations between silent nucleotide diversity and silent divergence, indicative of marked among-locus differences in mutation rates and/or selective constraints. Furthermore, using a physical estimate of local recombination rates, we find that silent nucleotide diversity (but not divergence) is positively correlated with recombination rate in two of the SI species. However, this correlation is not nearly as strong as in other well-characterized species (in particular, Drosophila). We propose that nucleotide diversity in Lycopersicon is dominated mainly by differences in neutral mutation rates and/or selective constraints among loci, demographic processes (such as population subdivision), and background selection. In addition, we hypothesize that the soil seed bank plays an important role in the maintenance of the large genetic diversity in the SI species (in particular L. peruvianum).

Base Sequence↗
PubMed2004

Impact of nonrandom mating on genetic variance and gene flow in populations with mass selection.

The mechanisms by which nonrandom mating affects selected populations are not completely understood and remain a subject of scientific debate in the development of tractable predictors of population characteristics. The main objective of this study was to provide a predictive model for the genetic variance and covariance among mates for traits subjected to directional selection in populations with nonrandom mating based on the pedigree. Stochastic simulations were used to check the validity of this model. Our predictions indicate that the positive covariance among mates that is expected to result with preferential mating of relatives can be severely overpredicted from neutral expectations. The covariance expected from neutral theory is offset by an opposing covariance between the genetic mean of an individual's family and the Mendelian sampling term of its mate. This mechanism was able to predict the reduction in covariance among mates that we observed in the simulated populations and, in consequence, the equilibrium genetic variance and expected long-term genetic contributions. Additionally, this study provided confirmatory evidence on the postulated relationships of long-term genetic contributions with both the rate of genetic gain and the rate of inbreeding (deltaF) with nonrandom mating. The coefficient of variation of the expected gene flow among individuals and deltaF was sensitive to nonrandom mating when heritability was low, but less so as heritability increased, and the theory developed in the study was sufficient to explain this phenomenon.

Genetic Variation↗
PubMed1999

Voluntary and involuntary sterilization: medical, ethical, legal and religious aspects.

Surgical voluntary sterilization has become one of the most widely used methods of contraception, with vasectomy and tubal sterilization being the most commonly employed techniques, associated with a low failure, morbidity, mortality, and long-term sequelae rate. As sterilization is related with the elimination of the possibility for procreation, a number of ethical, legal and religious issues have arisen, leading often to personal misjudgements, legal disputes, and failures in applying family planning. Involuntary sterilization is currently not practiced, except in cases of severely mentally retarded people, who are unable to appreciate the consequences of their acts or care for their children and who may have a high likelihood of propagating hereditary disease.

Ethics, Medical↗
PubMed2001

Reproductive health services and the law and ethics of conscientious objection.

Reproductive health services address contraception, sterilization and abortion, and new technologies such as gamete selection and manipulation, in vitro fertilization and surrogate motherhood. Artificial fertility control and medically assisted reproduction are opposed by conservative religions and philosophies, whose adherents may object to participation. Physicians' conscientious objection to non-lifesaving interventions in pregnancy have long been accepted. Nurses' claims are less recognized, allowing nonparticipation in abortions but not refusal of patient preparation and aftercare. Objections of others in health-related activities, such as serving meals to abortion patients and typing abortion referral letters, have been disallowed. Pharmacists may claim refusal rights over fulfilling prescriptions for emergency (post-coital) contraceptives and drugs for medical (i.e. non-surgical) abortion. This paper addresses limits to conscientious objection to participation in reproductive health services, and conditions to which rights of objection may be subject. Individuals have human rights to freedom of religious conscience, but institutions, as artificial legal persons, may not claim this right.

Abortion, Induced↗
PubMed1975

The mating system and microevolution.

Studies of natural and experimental plant populations have revealed that genotypic frequency distributions are highly structured in predominantly selfing species. This high degree of genetic organization is manifested in intense correlations in allelic state over loci and also in striking micro-geographical heterogeneity. Both aspects of this structure are facilitated by self-fertilization. Development of non-random associations of alleles within populations is facilitated because inbreeding reduces heterozygosity and thus also the randomizing effect of recombination. Spatial differentiation is facilitated because self-fertilization retards gene flow from population to population. The effect of organizing the entire populational genotype into a sort of giant supergene is to increase the frequency in the population of genotypes which confers high fitness and hence to increase adaptation to the local environment. However the recombinational potential remains substantial. As a result considerable free genetic variability remains in the population and it is available for long-term response to natural selection. Thus the organization of genetic variability within populations provides for high immediate fitness and also for flexibility to meet longer term evolutionary needs. At the same time selfing is a barrier to migration and it promotes the development and maintenance of different multilocus organizations in adjacent populations occupying unlike habitats. In total, therfore, a pattern of genetic differentiation develops in space which is an almost exact overlay of the environmental heterogeneity. The plant genetic and plant breeding literature contains extensive evidence that the mating system in plants can be modified simply and drastically by selection and that different populations within the same species often practice very different amounts of inbreeding. Considering the ease with which the mating system can be altered, and the benefits of adjusting genetic variability through regulation of the mating system, it is not surprising that a high proportion of flowering plants self-fertilize to some extent and that at least one-third of species have adopted predominant selfing as a strategy in ecogenetic adaptation.

Adaptation, Biological↗