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PubMed2005

Estimation of genetic parameters of semen characteristics and reproductive traits in AI boars.

(Co)variance components and further genetic parameters of boar semen characteristics and reproductive traits were estimated using the REML procedure applied to multi-trait animal models. The calculations were based on data from 210,733 ejaculates stemming from 2862 AI boars and collected from 1990 to 1997 in insemination stations for boars in the Czech Republic. Equal model equations for all traits included the AI station and the breed or breed combination as fixed effects, the interval between two collections for the boar as covariable and the animal and residual effects as random effects. The following heritabilities were estimated: semen volume 0.58, sperm concentration 0.49, progressive motion of spermatozoa 0.38, abnormal spermatozoa 0.34, number of total spermatozoa 0.42, number of insemination doses 0.40, number of piglets born alive 0.08, total number of piglets born 0.05 and conception rate 0.29. Heritabilities and genetic correlations were estimated on average values for each boar.

Animals↗
PubMed2001

Ethical regulation and the new reproductive technologies in Sri Lanka: perspectives of ethics committee members.

OBJECTIVE: To report on part of a pilot study done to explore ethical responses to the new reproductive technologies in Sri Lanka. DESIGN: Semi-structured interviews carried out with the members of three committees responsible for ethical review of medical research. Members were asked for their views on the ethical, social and legal implications of the new reproductive and genetic technologies. Members' responses were subject to a simple content analysis. CONCLUSIONS: There was broad acceptance of the new technologies among respondents, but anxieties about potential abuses. Respondents felt that a national committee should regulate practice and monitor future policy.

Attitude↗
PubMed2005

Encouraging science reading beyond the curriculum.

Students in genetics and reproductive physiology, junior-/senior-level courses with enrollments averaging 76 and 41 students, respectively, were encouraged to read popular science books for extra credit. The objectives of the readings were to reinforce basic class concepts by forming ties to everyday life, and to expose students to a genre that can provide information to prepare them as citizens to engage in the debate over current issues. The books for genetics were The Double Helix, Genome, Voyage of the Beagle, and The Engineer in the Garden; and the books for reproductive physiology were Clone, Lives of a Cell, Life Before Birth and A Time to be Born, and The Second Creation: Dolly and The Age of Biological Control. To earn credit (3% of the course grade for each of up to three books), students had to demonstrate knowledge and understanding of each book during a 15-min discussion with the instructor. Discussions focused on questions designed to stimulate critical thinking about each book's content. For example: "There is approximately 98% homology in DNA sequence between humans and chimpanzees; in aspects ranging from basic physiology to behavior, what makes us similar to or different from the species that is our closest living relative?" The numbers of students reading three books in Years 1 and 2 were 2 and 12 in genetics, and 4 and 3 in reproductive physiology; those reading two books in Years 1 and 2 were 5 and 20 in genetics, and 0 and 2 in reproductive physiology; and those reading one book in Years 1 and 2 were 21 and 31 in genetics, and 7 and 8 in reproductive physiology. The numbers of students that read no books in Years 1 and 2 were 33 and 27 in genetics, and 45 and 20 in reproductive physiology. Participation in the reading project occurred independently of course grades. Sixteen genetics students from the second year's class, eight that had participated in the extra credit reading and eight that had not, volunteered to be reexamined on material from the class. The reexamination was conducted 3 mo after the end of the class. With first exam score fitted as a covariate (P < 0.10), participation in the extra credit reading assignment did not affect score on the reexamination; participants averaged 67% correct answers, nonparticipants averaged 59% (P = 0.37). Comments on course evaluations indicated broad satisfaction with the assignments. Although no improvement of retention could be documented from this project, our objective of encouraging students to engage in reading material supplemental to courses in genetics and reproductive physiology was satisfied.

Curriculum↗
PubMed2003

A selfish origin for recombination.

Recent findings of molecular biology show that recombination is initiated by interactions between homologous chromosomes and that an allele can induce the initiation of recombination on the homolog. Since gene conversion at the site of initiation is strong enough to promote the transmission of that allele, recombination may be a way for a self-promoting element to spread, even if it gives no advantage to the individual or to the population. I develop a simple model and discuss available molecular evidence in support of this hypothesis. A consequent argument is that with asexual reproduction the evolution of recombination leads to an intragenomic conflict, and a possible outcome of this conflict may be the origin of sexual reproduction.

Animals↗
PubMed2004

A test of the chromosomal rearrangement model of speciation in Drosophila pseudoobscura.

Recent studies suggest that chromosomal rearrangements play a significant role in speciation by preventing recombination and maintaining species persistence despite interspecies gene flow. Factors conferring adaptation or reproductive isolation are maintained in rearranged regions in the face of hybridization, while such factors are eliminated from collinear regions. As a direct test of this rearrangement model, we evaluated the genetic basis of hybrid male sterility in a sympatric species pair, Drosophila pseudoobscura pseudoobscura and D. persimilis, and an allopatric species pair, D. pseudoobscura bogotana and D. persimilis. Our results are consistent with the proposed model: virtually all of the sterility factors in the former pair are associated with three inverted regions, whereas sterility factors are present in the collinear regions in the latter pair. These findings indicate recombination and selection may have eliminated sterility factors outside the inverted regions between D. p. pseudoobscura and D. persimilis, suggesting chromosomal rearrangements may facilitate species persistence despite hybridization.

Animals↗
PubMed1996

Genetic variation and covariation for ewe reproduction, lamb growth, and lamb scrotal circumference in a fall-lambing sheep flock.

Genetic parameters for female reproduction, lamb growth, and lamb scrotal circumference in a composite population of 50% Dorset, 25% Rambouillet and 25% Finnsheep breeding selected for ability to lamb in fall were estimated by REML using various animal models. Traits considered were spring fertility, litter size, weight at weaning (WWT), 90 d (WT90), and 120 d (WT120), and scrotal circumference at weaning (WSC), 90 d (SC90), and 120 d (SC120). Fertility was defined as 1 or 0 for ewes that lambed or failed to lamb, respectively, in fall and averaged .59 for adults (3 yr and older), .45 for second-lambing ewes, .18 for 19-mo-old ewes, and .11 for 12-mo-old ewes. Heritability estimates for fertility varied among models from .07 to .11. Heritability of fall litter size was .10. For body weights, estimates of additive direct, additive maternal, permanent environmental maternal, and litter effects as proportions of phenotypic variance were .04, .10, .05, and .11, respectively, for WWT, .09, .05, .14, and .01 for WT90, and .18, .0, .13, and .06 for WT120. Heritability estimates for WSC, SC90, and SC120 were .15, .25, and .02, respectively. Estimates of genetic correlations among body weights ranged from .77 to unity. Estimates of genetic correlations of fertility with fall litter size, WT90, and SC90 were .56, -.31, and .29, respectively. Genetic correlations of fall litter size with WT90 and SC90 were .33 and .36, respectively. Estimated genetic correlations revealed no major genetic antagonisms with ability to lamb in fall.

Animals↗
PubMed2005

Contemplating choice: attitudes towards intervening in human reproduction in Sri Lanka.

To date, relatively little is known about the ethical, legal and social responses to recent advances in reproductive and genetic technology outside Europe and North America. This article reports on a survey carried out among doctors (n=278) and medical students (n=1256) in Sri Lanka to find out more about their responses to novel interventions in human reproduction such as In-Vitro Fertilization, Pre-Implantation Genetic Diagnosis and genetic engineering. In the first part of the paper comparisons are drawn between this survey and a survey carried out in 1985 which also considered issues surrounding amniocentesis and therapeutic termination. The second part of the paper deals with more recent developments. The analysis reveals high levels of support for the use of new technologies in treating infertility and identifying genetic disorders. However, differences are apparent among the major religious communities represented in the sample and these are particularly in evidence in relation to prenatal genetic diagnosis. An important theme throughout both surveys is the continuing tension surrounding State policy and termination of pregnancy and the implications this has for the development of screening and counseling services where genetic disorders are concerned.

Abortion, Eugenic↗
PubMed2005

Reprogenetics and pharmacogenetics: in whose best interests?

Reprogenetics involves embryonic pre-implantation genetic diagnosis, provoking controversy over the creation of saviour siblings, eugenics and genetic enhancement. It will soon ascertain pharmacogenetic susceptibilities. Pharmacogenetics impacts upon public health initiatives underpinned by resource allocation constraints in that genetic epidemiological studies assist in administering health care resources and public health strategies. Knowing how likely sections of the population are to develop specific medical conditions so that lifestyle and environmental factors influencing these conditions can be targeted has the potential to save public money and improve public health. Aligning population groups with genetic susceptibilities with specific medications would enable cost-effective prescribing. Reprogenetics and pharmacogenetics also possess great commercial potential for nation states and biotechnology companies. Hence ethical legal safeguards for members of the public whose reproductive or genetic tissue is a research or health care resource are essential. Both legal measures such as informed consent and mechanisms for including the public in policy decisions over reprogenetics and pharmacogenetics must be rethought to ensure that they provide protection rather than function as rubber stamps which preclude deeper inquiry into justifications of projects.

Genetic Research↗
PubMed1998

Why sex and recombination?

REVIEW Most higher organisms reproduce sexually, despite the automatic reproductive advantage experienced by asexual variants. This implies the operation of selective forces that confer an advantage to sexuality and genetic recombination, at either the population or individual level. The effect of sex and recombination in breaking down negative correlations between favorable variants at different genetic loci, which increases the efficiency of natural selection, is likely to be a major factor favoring their evolution and maintenance. Various processes that can cause such an effect have been studied theoretically. It has, however, so far proved hard to discriminate among them empirically.

Animals↗
PubMed1989

[Polymorphism of alpha1-antitrypsin in Pamir populations. Reproductive compensation--possible mechanism for maintaining genetic diversity gor PI genes in human populations].

The distribution of the phenotype and gene frequencies of alpha 1-antitrypsin among Pamir's aborigines localized at high altitudes was studied. The Kirghizes of Murgab studied include mainly the mongoloid component in their composition. Populations of the Khuf river valley in West Pamir anthropologically belong to South caucasoids. The following frequencies of PI genes have been registered in Kirghizes (N = 102): M1 = 0.6961, M2 = 0.2108, M3 = 0.0539, Z = 0.0245, I = 0.0049, S = 0.0049, N = 0.0049; in the Khuf population (N = 122): M1 = 0.7910, M2 = 0.0943, M3 = 0.0984, Z = 0.0082, I = 0.0041, S = 0.0041; in the Pastkhuff population (N = 38): M1 = 0.7237, M2 = 0.1579, M3 = 0.1053, Z = 0.0132. A parallele biodemographic investigation in the Murgab population showed that couples, with one of the partners carrying the rare variant of PI demonstrated statistically significant increase in successful outcomes of pregnancies. The same cohort has displayed lower infant mortality rates, the absence of miscarried fetus and stillborn babies. Our results point to the possible existence of a mechanism of reproductive compensation serving to uphold the genetic diversity of PI genes.

Asian People↗
PubMed2003

[DNA polymorphism of Drosophila genes and factors determining it].

The data on variation of DNA sequences in genes of Drosophilidae are reviewed. Intraspecific polymorphism and interspecific divergence of DNA nucleotide sequences are shown to be characteristic of most genes. The level of intraspecific polymorphism and interspecific DNA divergence and the degree of correlation between them depend on the mode, intensity, and direction of natural selection, as well as on the evolutionary history of the genes and species. The evolutionary role of synonymous and nonsynonymous nucleotide substitutions in DNA is analyzed. Genes responsible for the reproduction and genes controlling other functions are compared in respect to their variation.

Animals↗
PubMed2006

Reproductive isolation due to the genetic incompatibilities between Thrichomys pachyurus and two subspecies of Thrichomys apereoides (Rodentia, Echimyidae).

We tested intrinsic reproductive isolation between 3 taxa of the South American caviomorph rodent Thrichomys (Rodentia, Echimyidae): T. pachyurus, T. apereoides subsp. apereoides and T. apereoides subsp. laurentius. They were mated in captivity and produced viable progeny. Some F1 hybrid females were fertile, whereas all F1 males were sterile. Histological examination revealed meiotic arrest at the primary spermatocyte stage. No sperm was detected in testes or epididymes. Electron microscopic analysis of surface spread synaptonemal complexes revealed a complete failure of chromosome pairing in F1 hybrids of T. pachyurus with T. apereoides subsp. laurentius and T. apereoides subsp. apereoides. In the male hybrids between T. apereoides subsp. apereoides and T. apereoides subsp. laurentius, meiosis did not proceed beyond diplotene, although all of the chromosomes, including heteromorphic ones, paired in an orderly fashion. Backcross males with homomorphic karyotypes showed segregation in meiosis progression. This indicates that male hybrid sterility is due to genetic, but not chromosomal, incompatibility of the parental taxa.

Animals↗
PubMed1994

Male mutation rates and the cost of sex for females.

Although we do not know why sex evolved, the twofold cost of meiosis for females provides a standard against which postulated benefits of sex can be evaluated. The most reliable benefit is sex's ability to reduce the impact of deleterious mutations. But deleterious mutations may themselves generate a large and previously overlooked female-specific cost of sex. DNA sequence comparisons have confirmed Haldane's suggestion that most mutations arise in the male germ line; recent estimates of a, the ratio of male to female mutation rates, are ten, six and two in humans, primates and rodents, respectively. Consequently, male gametes may give progeny more mutations than the associated sexual recombination eliminates. Here I describe computer stimulations showing that the cost of male mutations can easily exceed the benefits of recombination, causing females to produce fitter progeny by parthenogenesis than by mating. The persistence of sexual reproduction by females thus becomes even more problematic.

Animals↗
PubMedDate not supplied

The evolution of alternative reproductive strategies: fitness differential, heritability, and genetic correlation between the sexes.

Paternity analyses using molecular markers have become standard in studies of mating systems, parentage, and kinship. In systems where individuals exhibit alternative mating strategies, molecular analyses have been productively used to estimate the reproductive success of each behavioral type and hence the fitness consequences to each individual. Here we review the fitness results in a system of five alternative mating strategies present in one population of side-blotched lizards (Uta stansburiana). Males in this population adopt one of three behavioral strategies that differ in their degree of territoriality and mate guarding. In contrast, females adopt one of two strategies that differ in offspring quantity and quality. We use paternity analyses to estimate the fitness of each morph, the heritability of reproductive strategy, and the correlation in strategy between the sexes and discuss the implications of our findings for the evolution and maintenance of reproductive polymorphism in this and other systems.

Animals↗