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PubMed2005

The role of Haldane's rule in sex allocation.

Sex allocation theory predicts that parents should bias their reproductive investments toward the offspring sex generating the greatest fitness return. When females are the heterogametic sex (e.g., ZW in butterflies, some lizards, and birds), production of daughters is associated with an increased risk of offspring inviability due to the expression of paternal, detrimental recessives on the Z chromosome. Thus, daughters should primarily be produced when mating with partners of high genetic quality. When female sand lizards (Lacerta agilis) mate with genetically superior males, exhibiting high MHC Class I polymorphism, offspring sex ratios are biased towards daughters, possibly due to recruitment of more Z-carrying oocytes when females have assessed the genetic quality of their partners. If our study has general applicability across taxa, it predicts taxon-specific sex allocation effects depending on which sex is the heterogametic one.

Animals↗
PubMed2004

Seasonal affective disorder: a vestigial evolutionary advantage?

The typical symptoms of recurrent winter depression include lowered mood, lethargy, hypersomnia, social withdrawal, decreased libido, increased appetite and weight gain. Mild hypomania often occurs in spring and summer. It is argued that this pattern of attenuated hibernation constituted an adaptive evolutionary mechanism which enhanced the likelihood of reproductive success, most notably for females, among populations living at temperate latitudes. Women were more likely to become pregnant in the summer and thus to give birth at a time of year when their babies had a higher chance of survival. Winter depression symptoms also promoted healthier pregnancies and gave rise to enhanced female-male pair-bonding which improved the survival chances of both mothers and babies. Hypomania in spring and summer also served to increase the likelihood of procreation at the optimal time of year. In the modern era, it is probable that recurrent winter depression is becoming a reproductive disadvantage.

Adaptation, Physiological↗
PubMed1986

Alcoholism and antisocial personality. The sociobiology of an addiction.

Alcohol consumption may become adaptive from the evolutionary viewpoint when drinking settings and intoxication can be used to enhance the "cheating" reproductive strategy of antisocial personality disorder. This may explain the selective pressures leading to the association of familial alcoholism and antisocial personality disorder.

Adaptation, Physiological↗
PubMed1989

Quantitative genetic analysis of courtship and reproduction in female Drosophila melanogaster.

Three hundred mother-daughter pairs were analyzed for seven attributes related to courtship and reproduction. Only the lag time from first courtship to copulation was significantly heritable; genetic correlations involving this attribute were not significant. The genetic correlation between fertility and lag time to first courtship was negative and significant. However, this genetic correlation is expected to have little impact on the retention of additive genetic variance or on response to selection because it involves two attributes with low heritabilities. The pattern of phenotypic covariation among traits is largely explained by environmental causes and is consistent with that found in a previous analysis of father-son pairs (Gromko, 1987).

Alleles↗
PubMed2004

Seeking more goodly creatures.

In principle, genetic and reproductive technologies might allow "enhanced" children--with mental aptitudes and personal qualities improved beyond their expected abilities or even beyond humanity's normal range. Worry about a "brave new world" has already begun, but is that world imminent? And assuming that parents could choose traits for their children, would this be a bad thing? Many people think so for many different reasons, Henry Greely writes, but before we decide to regulate genetic enhancement, we need to decide how it differs from other forms of enhancement, traditional and new, and if those differences are important enough to justify regulation.

Coercion↗
PubMed1998

The application of genetic knowledge: ethical and policy implications.

This article explores societal ethical concerns about the application of the rapidly developing knowledge in the field of genetics. The article calls for nurses to reflect on these ethical concerns not only in the care of patients but also in professional and societal discussion, so that sound ethical and societally acceptable public policy can be adopted. A brief summary introduces the concepts of ethics and policy. The text than offers discussion of genetic testing for adults and children, testing in relation to behavioral attributes, and genetics and reproduction. Hypothetical cases using fictional names are used to illustrate each section. Recommendations for nurse action are cited. Finally, the article poses questions that require public awareness and discussion.

Adult↗
PubMed1994

Transposable elements as population drive mechanisms: specification of critical parameter values.

With a view to the possible use of transposable elements (TEs) as a mechanism to drive genes into insect vector populations, we used a three-parameter density dependent growth equation to examine the critical parameter values that determine whether or not a mobile element will spread and become fixed in a finite diploid vector population. Populations were simulated with parameter values affecting size, reproductive rate, density-dependence, and transposition efficiency of the mobile element. Simulations indicated that an equilibrium was reached quickly, typically in < 50 generations. Even when initially present at < or = 1% of a large population, the mobile element spread quickly and became fixed if transposition efficiency was equal to unity and infertility caused by the element decreased reproductive capacity by as much as 45%. These results were insensitive to the values of basic wild type reproductive rates and density dependence, but population size, transposition efficiency of the element, reproductive rate individuals bearing TEs and initial ratio of TE-bearing to wild individuals modified the outcome. As population size and transposition efficiency decreased in value, TEs became fixed less easily. However, even in populations as small as n = 100, an element with a transposition efficiency > 0.75 that reduces fertility < 25% will become fixed when introduced at a frequency as low as 1% of the total population. These results are consistent with previously reported population genetics models. They suggest that engineered transposons with a wide range of properties may be used to drive genes, such as those for parasite resistance, into wild vector populations.

Animals↗
PubMed2003

Population genetic consequences of extreme variation in sexual and clonal reproduction in an aquatic plant.

Most plants combine sexual reproduction with asexual clonal reproduction in varying degrees, yet the genetic consequences of reproductive variation remain poorly understood. The aquatic plant Butomus umbellatus exhibits striking reproductive variation related to ploidy. Diploids produce abundant viable seed whereas triploids are sexually sterile. Diploids also produce hundreds of tiny clonal bulbils, whereas triploids exhibit only limited clonal multiplication through rhizome fragmentation. We investigated whether this marked difference in reproductive strategy influences the diversity of genotypes within populations and their movement between populations by performing two large-scale population surveys (n = 58 populations) and assaying genotypic variation using random amplified polymorphic DNA (RAPDs). Contrary to expectations, sexually fertile populations did not exhibit higher genotypic diversity than sterile populations. For each cytotype, we detected one very common and widespread genotype. This would only occur with a very low probability (< 10-7) under regular sexual recombination. Compatibility analysis also indicated that the pattern of genotypic variation largely conformed to that expected with predominant clonal reproduction. The potential for recombination in diploids is not realized, possibly because seeds are outcompeted by bulbils for safe sites during establishment. We also failed to find evidence for more extensive movement of fertile than sterile genotypes. Aside from the few widespread genotypes, most were restricted to single populations. Genotypes in fertile populations were very strongly differentiated from those in sterile populations, suggesting that new triploids have not arisen during the colonization of North America. The colonization of North America involves two distinct forms of B. umbellatus that, despite striking reproductive differences, exhibit largely clonal population genetic structures.

Canada↗
PubMed2000

Genetic screening in patients of reproductive age. How do you advise prospective parents who want to know specific risks?

At times, determining the actual genetic condition occurring in a family can be very difficult. The most important steps in deciding when testing is appropriate are the patient's age and family history, with special attention to ethnic background. By identifying risk factors before pregnancy, prospective parents can be fully informed about their specific risk of having a child with a genetic condition. Furthermore, the pros and cons of invasive prenatal diagnostic procedures often can be fully discussed well in advance of an actual pregnancy. Clinical geneticists and genetic counselors can provide valuable assistance when difficult questions or problems arise.

Adult↗
PubMed1995

Genetic risk in micromanipulative assisted reproduction.

The empirical data on pregnancy outcome after intracytoplasmic sperm injection (ICSI) are encouraging, but still insufficient to rule out definitely adverse genetic or teratological effects. We analyse potential adverse effects of ICSI by applying general principles of genetic and teratological risk assessment. The role of gamete micromanipulation as a possible teratogen is discussed. We consider whether ICSI patients are at increased risk for carrying and propagating genetic lesions of different kinds. The possible interference of ICSI with genomic imprinting and pre-zygotic sperm selection is reviewed and we discuss the potentially protective role of DNA repair in oocytes. Considering the available empirical data and the conclusions from our theoretical analysis it appears that neither lassitude nor over-concern about adverse effects of ICSI are justified.

Congenital Abnormalities↗
PubMed1999

Theological issues in genetics.

Theological reflection can contribute a distinctive perspective from which to analyze and evaluate moral debates about issues in modern genetics and reproductive medicine. The author appeals to two hermeneutical themes, human beings as "images of God" and the tendency of humans to "play God," in order to discuss various church statements and theological literature on human gene transfer, somatic cell nuclear transplant cloning of human beings, and patenting of human genes.

Christianity↗
PubMed2005

Life-history evolution and the origin of multicellularity.

The fitness of an evolutionary individual can be understood in terms of its two basic components: survival and reproduction. As embodied in current theory, trade-offs between these fitness components drive the evolution of life-history traits in extant multicellular organisms. Here, we argue that the evolution of germ-soma specialization and the emergence of individuality at a new higher level during the transition from unicellular to multicellular organisms are also consequences of trade-offs between the two components of fitness-survival and reproduction. The models presented here explore fitness trade-offs at both the cell and group levels during the unicellular-multicellular transition. When the two components of fitness negatively covary at the lower level there is an enhanced fitness at the group level equal to the covariance of components at the lower level. We show that the group fitness trade-offs are initially determined by the cell level trade-offs. However, as the transition proceeds to multicellularity, the group level trade-offs depart from the cell level ones, because certain fitness advantages of cell specialization may be realized only by the group. The curvature of the trade-off between fitness components is a basic issue in life-history theory and we predict that this curvature is concave in single-celled organisms but becomes increasingly convex as group size increases in multicellular organisms. We argue that the increasingly convex curvature of the trade-off function is driven by the initial cost of reproduction to survival which increases as group size increases. To illustrate the principles and conclusions of the model, we consider aspects of the biology of the volvocine green algae, which contain both unicellular and multicellular members.

Animals↗
PubMed2004

Natural variation in expression of self-incompatibility in Arabidopsis thaliana: implications for the evolution of selfing.

The switch from an out-crossing to a self-fertilizing mating system is one of the most prevalent evolutionary trends in plant reproduction and is thought to have occurred repeatedly in flowering plants. However, little is known about the evolution of self-fertility and the genetic architecture of selfing. Here, we establish Arabidopsis thaliana as a model for genetic analysis of the switch to self-fertility in the crucifer family, where the ancestral out-crossing mode of mating is determined by self-incompatibility (SI), a genetic system controlled by the S locus. We show that A. thaliana ecotypes exhibit S-locus polymorphisms and differ in their ability to express the SI trait upon transformation with S-locus genes derived from the obligate out-crosser Arabidopsis lyrata. Remarkably, at least one ecotype was reverted to a stable, self-incompatible phenotype identical to that of naturally self-incompatible species. These ecotype differences are heritable and reflect the fixation in different A. thaliana populations of independent mutations that caused or enforced the switch to self-fertility. Their continued analysis promises to identify the loci that were the targets of natural selection for selfing and to contribute to a mechanistic understanding of the SI response.

Arabidopsis↗
PubMedDate not supplied

Comparison of cellular and whole-animal bioassays for estimation of radiation effects in the polychaete worm Neanthes arenaceodentata (Polychaeta).

The polychaete worm Neanthes arenaceodentata was used in experiments to determine possible relationships between short-term genotoxicity tests and reproductive and lethal consequences of exposure to ionizing radiation. Groups of juvenile N. arenaceodentata received one of four different radiation doses (2, 4, 8, and 16 Gy) to determine dose-effect estimates for chromosomal aberration induction, and groups of both adult and juveniles received one of seven different radiation doses (1, 4, 8.4, 46, 102, 500, and 1000 Gy) to determine dose-effect estimates for reproduction, mortality, and life span. Effects on reproduction and genetic material were observed at the lowest doses and in the same range; detrimental reproductive effects were observed at 1 to 4 Gy, and the frequency of chromosomal aberrations was significantly increased at 2 Gy. Only high doses resulted in acute mortality (greater than 500 Gy) and decreased life span (greater than 100 Gy). Dose-effect estimates for chromosomal aberration induction were dependent on radiation dose and on the stage of the cell cycle at the time of irradiation. Dose-effect estimates for reproduction were dependent on dose and the potential for repopulation of gonadal tissue. It is concluded that short-term genotoxicity test can be predictive of detrimental reproductive effects in those model systems for which basic cell kinetics and reproductive parameters are well known.

Animals↗
PubMed2004

The F-box protein AhSLF-S2 controls the pollen function of S-RNase-based self-incompatibility.

Recently, we have provided evidence that the polymorphic self-incompatibility (S) locus-encoded F-box (SLF) protein AhSLF-S(2) plays a role in mediating a selective S-RNase destruction during the self-incompatible response in Antirrhinum hispanicum. To investigate its role further, we first transformed a transformation-competent artificial chromosome clone (TAC26) containing both AhSLF-S(2) and AhS(2)-RNase into a self-incompatible (SI) line of Petunia hybrida. Molecular analyses showed that both genes are correctly expressed in pollen and pistil in four independent transgenic lines of petunia. Pollination tests indicated that all four lines became self-compatible because of the specific loss of the pollen function of SI. This alteration was transmitted stably into the T1 progeny. We then transformed AhSLF-S(2) cDNA under the control of a tomato (Lycopersicon esculentum) pollen-specific promoter LAT52 into the self-incompatible petunia line. Molecular studies revealed that AhSLF-S(2) is specifically expressed in pollen of five independent transgenic plants. Pollination tests showed that they also had lost the pollen function of SI. Importantly, expression of endogenous SLF or SLF-like genes was not altered in these transgenic plants. These results phenocopy a well-known phenomenon called competitive interaction whereby the presence of two different pollen S alleles within pollen leads to the breakdown of the pollen function of SI in several solanaceaous species. Furthermore, we demonstrated that AhSLF-S(2) physically interacts with PhS(3)-RNase from the P. hybrida line used for transformation. Together with the recent demonstration of PiSLF as the pollen determinant in P. inflata, these results provide direct evidence that the polymorphic SLF including AhSLF-S(2) controls the pollen function of S-RNase-based self-incompatibility.

Amino Acid Sequence↗