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Comparison of Henderson's Method I and restricted maximum likelihood estimation of genetic parameters of reproductive traits.

Genetic parameters of simulated reproductive traits were estimated with Henderson's Method I or restricted maximum likelihood (REML). Each of the 25 samples consisted of 2,667 birds from 50 sires. When reproductive traits were measured on all birds, the means of both sets of estimates were equal to the true value; however, precision was higher with REML. When they were only measured on the 60 (20%) heaviest birds, Henderson's Method I was severely biased by selection (up to 40% for estimates of heritability of reproductive traits and up to 45% for estimates of genetic correlation between reproductive traits and body weight). This bias, as well as the variance of estimates, increased with selection rate and absolute value of genetic correlation between body weight and reproductive traits (or another criterion of selection). Conversely, REML was not biased by selection. It should therefore be preferred when sequential selection occurs.

Analysis of Variance↗

Public deliberation and private choice in genetics and reproduction.

The development of human genetics raises a wide range of important ethical questions for us all. The interpersonal dimension of genetic information in particular means that genetics also poses important challenges to the idea of patient-centredness and autonomy in medicine. How ought practical ethical decisions about the new genetics be made given that we appear, moreover, no longer to be able to appeal to unquestioned traditions and widely shared communitarian values? This paper argues that any coherent ethical approach to these questions must be able both to uphold the moral status of the individual and at the same time recognise the communitarian, interpersonal dimensions both of the world in which we live and of personal autonomy itself. The paper then goes on to propose an approach to the resolution of the ethical questions raised by the use of the new genetics in reproductive choice through the development of a coherent and principled process of public reason and justification oriented towards the support and development of personal autonomy.

Ethics, Medical↗

Genome mapping in ruminants and map locations for genes influencing reproduction.

Genetic maps provide a critical link between genes and phenotypes and are essential tools in the search for the genetic basis of variation in reproductive traits. Genes coding for hormones, growth factors, receptors, binding proteins, transcription factors and enzymes that influence the development and function of the reproductive axis have been assigned to genetic maps of ruminants and locations can be found in the respective genome databases. In addition, comparative information on gene structure and map location will help define the functions of essential genes. Gene locations from other species can be used because of extensive comparative links among mammalian gene maps. Large-scale projects to sequence genes and the ability to map these genes in parallel in radiation hybrid panels of different species will greatly improve the maps and our ability to translate between them. Cloning the genes responsible for genetic differences in fertility and fecundity in ruminants is likely to provide valuable clues to understanding ovarian function and germ cell development.

Animals↗

Assisted reproductive technologies: genetic and nursing implications.

The convergence of the fields of clinical genetics and assisted reproductive technologies is providing couples at risk for transmitting a genetic disorder to their children with new reproductive alternatives. The ability to test the preimplantation embryo for genetic anomalies, sort for X- and Y-bearing sperm, and improve genetic screening of gamete donors and couples at risk for a genetic disorder, are examples of these alternatives. The scope of nursing practice will be affected by the integration of these technologies into the health care offered to consumers. Opportunities also will exist for nurses to assist in the redefinition of health and illness that will be the serendipitous outcome of these scientific advances.

Genetic Testing↗

Sex and death in the mouse: genetically delayed reproduction and senescence.

A mammalian model of genetically postponed aging would be an important tool to test not only different mechanisms of aging but also the predictive value of various biomarkers of the aging process. Under conventional conditions, the historical strains of the laboratory mouse produce their first litter between 9 and 13 weeks of age and have a median time of death in their 2nd year. Our POSCH-2 strain, which was derived from wild-caught Mus musculus domesticus, produces its first litter in the current breeding generations at approximately 47 weeks of age and continues to breed throughout its 2nd and into its 3rd year of life. The aging curve of POSCH-2 has not yet been determined for economic reasons. Late onset of breeding is a characteristic of both females and males, but sexual maturity is more reliably assessed in females. The later breeding phenotype of POSCH-2 is genetically recessive to early breeding of the C57BL/6J historical laboratory strain and, since POSCH-2 females can be induced to ovulate at 8 weeks of age (but pregnancy does not result), the signal rather than the ovarian receptor to ovulate may be delayed. The genetically delayed reproduction and potentially longer life of the POSCH-2 strain appears to be a new trait in the mouse. The strain may be a useful mammalian model for aging studies and for the evaluation of antagonistic pleiotropy as a genetic model for the evolution of aging.

Aging↗

Advances in the genetics of reproductive isolation in Drosophila.

Speciation genetics is defined as the study of genetic events and processes that differentiate the probabilities that genetic material from individual members of a population will co-occur in individuals of some future generation. It follows that phenotypic attributes that contribute to this differentiation of probabilities (e.g., mating preferences, sterility, or infertility of individuals from certain types of matings) constitute the phenotype of speciation, and genetic loci that may affect these phenotypic attributes can be considered as speciation genes. The literature on genetic differences between hybridizable species of Drosophila that are responsible for morphological differences, mating preferences, hybrid inviability, and hybrid sterility are reviewed with special reference to the species pair D. mojavensis - D. arizonensis. The case for the involvement of karyotypic changes in speciation in rodents is briefly discussed. It is concluded that no major advance has been made in the speciation genetics of Drosophila since Dobzhansky initiated the field 40 years ago. Yet, the identification of several gene loci that cause hybrid inviability or sterility may open the way to the understanding of reproductive isolation at the molecular level. It is not clear whether this approach will lead to general molecular mechanisms underlying the speciation process.

Animals↗

Genetics and reproduction in fish culture.

Fish genetics has made major strides during the past 20 yr due both to improvements in the ability of fish culturists to manage reproduction and to deliberate experimentation and application. The general finding has been that the quantitative genetics of fish differ little from those of other animals and that the applications of animal improvement techniques are similar for fish and other animals. In addition, a number of novel techniques, such as ploidy manipulation and sex reversal, are relatively easy to achieve with a number of fish species. As a result, some very specialized approaches to research have been possible, and applications to fish production seem to be limited only to the imagination of the breeder. However, only limited application has occurred over a major portion of the industry, and genetic improvement of stocks has been achieved in very few instances. The reason for this apparent dichotomy between opportunity and reality seems to be related to the industry's lack of emphasis on genetic improvement.

Agriculture↗

Evidence for the evolution of bdelloid rotifers without sexual reproduction or genetic exchange.

The Class Bdelloidea of the Phylum Rotifera is the largest metazoan taxon in which males, hermaphrodites, and meiosis are unknown. We conducted a molecular genetic test of this indication that bdelloid rotifers may have evolved without sexual reproduction or genetic exchange. The test is based on the expectation that after millions of years without these processes, genomes will no longer contain pairs of closely similar haplotypes and instead will contain highly divergent descendants of formerly allelic nucleotide sequences. We find that genomes of individual bdelloid rotifers, representing four different species, appear to lack pairs of closely similar sequences and contain representatives of two ancient lineages that began to diverge before the bdelloid radiation many millions of years ago when sexual reproduction and genetic exchange may have ceased.

Animals↗

Prenatal diagnosis, genetics and reproductive decision-making.

Recent developments in genetic science will potentially have a significant impact on reproductive decision-making by adding to the list of conditions which can be diagnosed through prenatal diagnosis. This article analyses the jurisdictional variations that exist in Australian abortion laws and examines the extent to which Australian abortion laws specifically provide for termination of pregnancy on the grounds of fetal disability. The article also examines the potential impact of pre-implantation genetic diagnosis on reproductive decision-making and considers the meaning of reproductive autonomy in the context of the new genetics.

Abortion, Eugenic↗

Wnt genes and endocrine disruption of the female reproductive tract: a genetic approach.

Reproductive tract development and function is regulated by circulating steroid hormones. In the mammalian female reproductive tract, estrogenic compounds direct many aspects of cytodifferentiation including uterine gland formation, smooth muscle morphology, and epithelial differentiation. While it is clear that these hormones act through their cognate nuclear receptors, it is less clear what signaling events follow hormonal stimulation that govern cytodifferentiation. Recent advances in molecular embryology and cancer cell biology have identified the Wnt family of secreted signaling molecules. Discussed here are recent advances that point to a definitive role during uterine development and adult function for one member of the Wnt gene family, Wnt-7a. In addition, recent data is reviewed that implicates Wnt-7a deregulation in response to pre-natal exposure to the synthetic estrogenic compound, DES. These advances point to an important role for the Wnt gene family in various reproductive tract pathologies including cancer.

Animals↗

A comparative study of ejaculate traits in three endangered ungulates with different levels of inbreeding: fluctuating asymmetry as an indicator of reproductive and genetic stress.

We studied three closely related species of endangered gazelles (Gazella dorcas, Gazella dama and Gazella cuvieri) with different levels of inbreeding in order to determine at which intensities inbreeding influences ejaculate traits. We also examined whether fluctuating asymmetry (FA) is a reliable indicator of genetic as well as reproductive stress. Our results show that, within each population, the individual coefficient of inbreeding is inversely related to ejaculate quality only in the species with the highest levels of inbreeding (G. cuvieri). In addition, FA is a reliable indicator of individual levels of inbreeding in both the species with the highest levels of inbreeding (G. cuvieri) and the species with intermediate levels of inbreeding (G. dama). Thus, FA appears in individuals whose levels of inbreeding are still not high enough to affect male reproductive potential and should therefore be considered a sensitive indicator of genetic stress. Finally, FA is also a reliable indicator of male reproductive stress since it is related to individual semen quality in all the species studied.

Animals↗

[Ethical problems in genetics and reproduction medicine].

Novel knowledge in the fields of molecular biology, genetics and reproductive medicine will revolutionize medicine in the near future. Among many new therapeutical aspects arise a number ethical questions that include preimplantation diagnostics, embryonic stem cell research and gene therapy. Believing in scientific progress is often criticized but today it is primarily ignorance as well as fundamentalism that block sensible discussions. In the future it shall be of importance to differentiate between "to be alive" and "to have a life", hence yielding a new definition of the term "life". Also important is to keep in mind the difference between individual moral claims and general ethics. Without doubt, the current developments in medicine will bring about interesting consequences but the inherent dangers are recognizable as well. However, only a positive attitude will result in beneficial developments. More flexibility on all sides will be needed in the concurrent discussion process.

Ethics, Clinical↗

Genetics of reproduction in primiparous Holsteins.

Effects of genetics and relationships between yield and days from parturition to first service, first service conception rate, number of services, and a reproductive performance code based on several reproductive components were investigated in primiparous Holsteins. Recorded breedings and DHI production records were from 3393 daughters of 174 bulls in six experimental herds. Subsets included progeny of 78 sires, with greater than or equal to 5 daughters calving in April through July (n = 817) and August through March (n = 1162). Daughter-dam regressions (n = 2593 pairs) and paternal half-sibs were used to estimate heritabilities of fertility traits and associations between yield and reproduction. Results showed increased FCM was associated with lowered fertility. For paternal half-sibs, the greatest antagonism was between conception rates and FCM (rG = -.65 +/- .10). Daughter-dam regressions estimated a favorable genetic correlation of .43 +/- .32 between conception rates and yield. Heritabilities were highest for April through July calvings and ranged from .08 +/- .10 for first service conception to .24 +/- .12 for reproductive code. Correlations between sire least squares constants from warmer and cooler calving seasons were lower than heritabilities of traits would suggest.

Animals↗

Genetic counseling for familial conditions during pregnancy: an analysis of patient characteristics.

Reproductive genetic counseling for a familial genetic risk factor preferably takes place before conception. However, of the women with a family history of genetic conditions who attend our department of clinical genetics, about 10-20% attend for the first time during a pregnancy. The current study aims to explore patient-related factors that may affect this late timing of reproductive genetic counseling. Consecutive pregnant (n = 100) and non-pregnant (n = 84) women visiting the department of clinical genetics for a genetic risk factor which was not age related completed a questionnaire immediately prior to the consultation. The questionnaire asked for (a) background characteristics, i.e. socio-demographic, obstetric, and disease characteristics (b) cognitive factors, i.e. initiative of referral, knowledge of the risk factor involved, risk perception, worry, child wish, attitudes toward abortion, and preferred participation in decision making, and (c) reasons for the timing of the consultation and for seeking genetic counseling. Pregnant women appeared to be higher educated, considered their children more often as healthy and were less often affected themselves, as compared to non-pregnant women. They also estimated their chance of having an affected child as lower, and they worried less. Furthermore, the initiative for referral was taken less often by the pregnant woman herself and more often by a medical worker. There were no major differences between the two study groups in knowledge, perceived severity of the risk factor, child wish, attitudes toward abortion, desired participation in decision making, and reasons to seek genetic counseling. Women indicated no specific reasons for their timing of referral for reproductive genetic counseling, e.g. during vs before pregnancy. Our data suggest that this timing of referral is not influenced predominantly by the women's level of knowledge. Rather, women's estimation of genetic risks and their degree of worry, which may be in accordance with the actual risk figures, seem to play a role in seeking genetic counseling. Although further studies are required, a more active role of health care providers seems warranted if we want to prevent genetic counseling for familial genetic conditions during pregnancy as much as possible.

Attitude to Health↗

Spinocerebellar ataxia in a large kindred: age at onset, reproduction, and genetic linkage studies.

We studied a large kindred with autosomal dominant spinocerebellar ataxia (SCA) to assess reproductive performance, the impact of genetic counseling, and linkage relationships of the SCA locus. Reproduction was not lower in those with SCA than in unaffected sibs or first cousins. Genetic counseling reduced reproduction during the risk period for development of SCA. Given autosomal dominant transmission of a single gene, we found strong evidence that the locus for SCA in this kindred is linked to the HLA loci.

Adolescent↗