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PubMed2006

The genomic era and perceptions of psychotic disorders: genetic risk estimation, associations with reproductive decisions and views about predictive testing.

As a result of publicity surrounding genetic advances, increasing public awareness of a genetic role in major mental illness may be contributing to a "geneticization" of these illnesses. Geneticization could lead to oversimplified ideas about genetic risk, producing significant social consequences. We sought to investigate perceptions of genetic risk, associated effects on reproductive decisions and attitudes towards genetic testing amongst unaffected relatives of individuals with psychosis. A web-based survey design was used, which all visitors to a psychosis support/information website had the option to complete. Responders were representative of website visitors, and the study design facilitated collection of a large dataset, although the response rate was low. Over-estimating risk was associated with reproductive decisions favoring fewer children, and more positive attitudes towards genetic testing. Facilitating accurate risk perception through genetic counseling could significantly impact reproductive decisions, and the appropriate use of genetic tests in the future.

Adult↗
PubMed2000

Genetic evidence for gonochoristic reproduction in gynogenetic silver crucian carp (Carassius auratus gibelio bloch) as revealed by RAPD assays.

Sex evolution has been a debating focus in evolutionary genetics. In lower vertebrates of reptiles, amphibians, and fish, a species or a bioform reproduces either sexually or asexually but never both. A few species were found to consist of all females in fish. These all-female species can propagate by asexual reproduction modes, such as gynogenesis and hybridogenesis. However, the coexistence of sexuality and asexuality in a single species was recently noted only in a cyprinid fish silver crucian carp, Carassius auratus gibelio. This fish had been demonstrated to be capable of gynogenesis stimulated by sperm from other related species. Surprisingly, natural populations of this fish consist of a minor but significant portion (approx. 20%) of males. As different clones with specific phenotypic and genetic characteristics have been found, and RAPD markers specific to each clone have recently been identified, this fish offers many advantages for analyzing whether or not genetic recombination occurs between different clones. In this study, artificial propagation was performed in clone F and clone D. Ovulated eggs from clone F were divided into two parts and respectively inseminated with sperm from a clone D male and from a red common carp (Cyprinus carpio) male. The control clone D individuals were selected from gynogenetic offspring of clone D activated by sperm of red common carp. The phenotype and sex ratio in the experimental groups were also observed. Using RAPD molecular markers, which allow for reliable discrimination and genetic analysis of different clones, we have revealed direct molecular evidence for gonochoristic reproduction in the gynogenetic silver crucian carp and confirmed a previous hypothesis that the silver crucian carp might reproduce both gynogenetically and gonochoristically. Therefore, we conclude that the silver crucian carp possesses two reproductive modes, i.e., gynogenetic and gonochoristic reproduction. The response mechanism of two reproductive development modes may be the first discovery in vertebrates. Additionally, we discuss the evolutionary implication between gynogenetic and gonochoristic reproduction modes and the contribution of the minor proportion of males to genetic flexibility in the gynogenetic silver crucian carp.

Animals↗
PubMed2025

Genetic structuring and estimation of reproductive adults in Onchocerca volvulus: A genome-wide analysis across hosts and regions.

Genomic analysis of parasites can deepen our understanding of their transmission, population structure, and important biological characteristics. Onchocerciasis (river blindness), caused by the parasitic nematode Onchocerca volvulus, involves adult worms residing in subcutaneous nodules that produce larval-stage microfilariae (mf), which are routinely detected in the skin for diagnosis. Whole-genome studies of mf are limited; most analyses have focused on the mitochondrial genome. We conducted a genome-wide analysis with 94% median nuclear genome coverage, analyzing 171, 37, and 98 mf from 16, 3, and 5 individuals from Ghana, Liberia, and the Democratic Republic of Congo, respectively. These data were used to investigate population differentiation, estimate the number of reproductive adult worms, and analyze genetic variation across chromosomes. Population genetic analyses across hosts and countries showed that nuclear genome diversity can reveal fine-scale genetic structure, even between geographically close countries, providing more resolution than mitochondrial haplotype data. By reconstructing maternal and paternal sibships, we estimated the number of reproductively active adult filariae. Comparisons between adult worm estimates from genetic data and nodule observations showed that genetics-based estimates were higher or equal to observed worm counts in 8 out of 9 hosts for female worms and 7 out of 9 hosts for male worms. Our analysis also revealed lower-than-expected X chromosome diversity, consistent with neo-X chromosome fusions in filarial species. This study represents an important step in using nuclear genome data from mf to support onchocerciasis elimination efforts and in developing genetic tools that could inform mass drug administration programs.

Onchocerca volvulus↗
PubMed2003

Reproductive character displacement and the genetics of gamete recognition in tropical sea urchins.

Reproductive character displacement occurs when sympatric and allopatric populations of a species differ in traits crucial to reproduction, and it is commonly thought of as a signal of selection acting to limit hybridization. Most documented cases of reproductive character displacement involve characters that are poorly understood at the genetic level, and rejecting alternative hypotheses for biogeographic shifts in reproductive traits is often very difficult. In sea urchins, the gamete recognition protein bindin evolves under positive selection when species are broadly sympatric, suggesting character displacement may be operating in this system. We sampled sympatric and allopatric populations of two species in the sea urchin genus Echinometra for variation in bindin and for the mitochondrial cytochrome oxidase I to examine patterns of population differentiation and molecular evolution at a reproductive gene. We found a major shift in bindin alleles between central Pacific (allopatric) and western Pacific (sympatric) populations of E. oblonga. Allopatric populations of E. oblonga are polyphyletic with E. sp. C at bindin, whereas sympatric populations of the two species are reciprocally monophyletic. There is a strong signal of positive selection (P(N)/P(S) = 4.5) in the variable region of the first exon of bindin, which is associated with alleles found in sympatric populations of E. oblonga. These results indicate that there is a strong pattern of reproductive character displacement between E. oblonga and E. sp. C and that the divergence is driven by selection. There is much higher population structure in sympatric populations at the bindin locus than at the neutral mitochondrial locus, but this difference is not seen in allopatric populations. These data suggest a pattern of speciation driven by selection for local gamete coevolution as a result of interactions between sympatric species. Although this pattern is highly suggestive of speciation by reinforcement, further research into hybrid fitness and egg-sperm interactions is required to address this potential mechanism for character displacement.

Amino Acid Sequence↗
PubMed1982

A controlled retrospective follow-up study of the impact of genetic counseling on parental reproduction following the birth of a Down syndrome child.

Twenty-three couples who had received genetic counseling after the birth of a Down Syndrome child (DSC) were closely match-paired by race, religion, maternal age, paternal occupation, parental education and sex sibship order of the DSC with 23 non-counseled couples who had also had a DSC. When evaluated at least 1 1/2 years after the birth of the DSC or the genetic counseling, there were no significant differences between counseled and non-counseled couples in knowledge of general genetics or recurrent risks for Down Syndrome, initiation of subsequent pregnancies, or utilization of prenatal diagnosis. Knowledge of general genetics and recurrent risks for Down Syndrome among our post-counselees was poorer than that of two published immediate follow-up reports. Although 18 of 46 couples initiated at least one more pregnancy after the birth of their DSC, only three couples (2 counseled; 1 non-counseled) utilized prenatal diagnosis by amniocentesis.

Adult↗
PubMed2006

Genetic analysis of male reproductive success in relation to density in the zebrafish, Danio rerio.

BACKGROUND: We used behavioural and genetic data to investigate the effects of density on male reproductive success in the zebrafish, Danio rerio. Based on previous measurements of aggression and courtship behaviour by territorial males, we predicted that they would sire more offspring than non-territorial males. RESULTS: Microsatellite analysis of paternity showed that at low densities territorial males had higher reproductive success than non-territorial males. However, at high density territorial males were no more successful than non-territorials and the sex difference in the opportunity for sexual selection, based on the parameter Imates, was low. CONCLUSION: Male zebrafish exhibit two distinct mating tactics; territoriality and active pursuit of females. Male reproductive success is density dependent and the opportunity for sexual selection appears to be weak in this species.

Journal Article↗
PubMed1996

Morphological-cytochemical and molecular genetic analyses of mitochondria in isolated human oocytes in the reproductive age.

Molecular genetic, cytochemical and morphometric analyses have been performed on isolated oocytes from 41 women (27-39 years of age) in order to detect mutations of mitochondrial DNA (mtDNA), defects of the respiratory chain (ubiquinone-cytochrome-c-oxidoreductase = complex III; cytochrome-c-oxidase = complex IV) and alterations of mitochondrial volume during cellular ageing. Morphometric analyses showed an increase in mitochondrial numerical density with age from the mean values of 7.36 per micron2 and 6.97 per micron3 up to 30 years to 10.74 per micron2 and 11.66 per micron3 in the age group 31-40 years (P < 0.001). Similarly, an increase in the mitochondrial profile area from 0.074 per micron2 in the age group < 30 years to 0.101 per micron2 was noted in the fourth decade. The mitochondrial volume fraction was also significantly increased in the elder age group. Neither point mutations of mtDNA (nucleotide pairs 3243, 8344) nor the common deletion (4977 bp, nucleotide pairs 8482-13460) could be detected. In parallel, ultra- and immunocytochemical studies of the complexes III-IV failed to reveal functional defects. In conclusion there is an age-related increase in the volume fraction of the mitochondria which might reflect subtle changes in the oxidative phosphorylation capacity, but is not linked to mutations of mtDNA or functional defects of the respiratory chain enzymes in mature human oocytes from women of reproductive age.

Adult↗
PubMed2005

Interannual genetic heterogeneity of pollen pools accepted by Quercus salicina individuals.

Since flowering often varies among years in wind-pollinated woody species, the genetic composition of pollen pools accepted by seed parents can differ between years. The interannual heterogeneity of pollen flow may be important for maintaining genetic diversity within populations because it can increase genetic variation within populations and the effective sizes of the populations. In this study we examined heterogeneity, using paternity analysis and analysis of molecular variance, in the genetic composition of pollen pools among different reproductive years for six Quercus salicina seed parents in an 11.56-ha plot in a temperate old-growth evergreen broadleaved forest. The genotypes at seven microsatellite loci were determined for 111 adult trees and 777 offspring of the six seed parents in 2-5 reproductive years. Genetic differentiation of pollen pools among different reproductive years for each seed parent was significant over all seed parents and for each of four seed parents that were analysed for more than 2 years, but not for either of the other two seed parents (analysed for 2 years). For both the pollen pools originating from inside the plot and those originating from outside it, genetic differentiation among different reproductive years for each seed parent was significant over all seed parents. However, among-year genetic differentiation in the pollen pools originating from within the plot was detected for all four of the seed parents that were analysed for more than 2 years, but for only one of the four in the pools originating from outside the plot. Genetic diversity (estimated as allelic richness and gene diversity) was higher for pollen pools over all reproductive years than for pollen pools in single years. These results indicate that the year-to-year genetic variation of pollen pools increases genetic diversity in offspring and is strongly affected by the variation in pollen parents within the plot because of their high pollination contributions. The high year-to-year variation in pollen parents within the plot and overall supports the hypothesis that the offspring produced across years represent a larger genetic neighbourhood.

Analysis of Variance↗
PubMed2004

Environmental causes of human congenital malformations: the pediatrician's role in dealing with these complex clinical problems caused by a multiplicity of environmental and genetic factors.

There have been amazing advances in embryology, teratology, reproductive biology, genetics, and epidemiology in the past 50 years that have provided scientists and clinicians with a better perspective on the causes of congenital malformations. We still cannot provide the families of children with malformations a definitive diagnosis and cause in every instance. The purpose of this article is to inform pediatricians about environmental drugs, chemicals, and physical agents that have been documented to produce congenital malformations and reproductive effects and to indicate that the multitude of teratogenic agents account for only a small proportion of malformations. The most common known cause is genetic, but the largest group, unfortunately, There have been amazing advances in embryology, teratology, reproductive biology, genetics, and epidemiology in the past 50 years that have provided scientists and clinicians with a better perspective on the causes of congenital malformations. We still cannot provide the families of children with malformations a definitive diagnosis and cause in every instance. The purpose of this article is to inform pediatricians about environmental drugs, chemicals, and physical agents that have been documented to produce congenital malformations and reproductive effects and to indicate that the multitude of teratogenic agents account for only a small proportion of malformations. The most common known cause is genetic, but the largest group, unfortunately, is unknown. There are a number of important clinical rules that are important for clinicians to use when determining the cause of their patient's congenital malformations: 1. No teratogenic agent should be described qualitatively as a teratogen, because a teratogenic exposure includes not only the agent but also the dose and the time in pregnancy when the exposure has to occur. 2. Even agents that have been demonstrated to result in malformations cannot produce every type of malformation. Known teratogens may be presumptively implicated by the spectrum of malformations that they produce. It is easier to exclude an agent as a cause of birth defects than to conclude definitively that it was responsible for birth defects, because of the existence of genocopies of some teratogenic syndromes. 3. When evaluating the risk of exposures, the dose is a crucial component in determining the risk. Teratogenic agents follow a toxicologic dose-response curve. This means that each teratogen has a threshold dose below which there is no risk of teratogenesis, no matter when in pregnancy the exposure occurred. 4. The evaluation of a child with congenital malformations cannot be performed adequately unless it is approached with the same scholarship and intensity as the evaluation of any other complicated medical problem. 5. Each physician must recognize the consequences of providing erroneous reproductive risks to pregnant women who are exposed to drugs and chemicals during pregnancy or alleging that a child's malformations are attributable to an environmental agent without performing a complete and scholarly evaluation. 6. Unfortunately, clinical teratology and clinical genetics is not emphasized in medical school and residency education programs, but pediatricians have a multitude of educational aids to assist them in their evaluations, which includes consultations with clinical teratologists and geneticists, the medical literature, and the OMIM web site.

Abnormalities, Drug-Induced↗
PubMed1984

Genetics of growth and reproduction in the turkey. 9. Long-term selection for increased 16-week body weight.

Sixteen generations of selection of turkeys for increased 16-week body weight alone resulted in a large increase in body weight at 8, 16, 20, and 24 weeks of age of both males and females and at sexual maturity for females. The realized heritability for 16-week body weight was .29 +/- .02 for males and .24 +/- .01 for females. There was no significant effect on egg production during the first three generations of selection. However, egg production of the growth strain relative to the corresponding randombred control declined greatly during the next two generations. Eleven further generations of selection did not result in additional declines in egg production. These results suggest that the genetic correlation between 16-week body weight and egg production was zero initially, became strongly negative for Generations 4 and 5, and then ultimately returned to zero. Genetic increases in body weight were associated with decreases in intensity of lay with no effect on broodiness. Based on a subjective rating of deviation of legs and ability to walk, the legs of the growth strain were poorer than those of its corresponding randombred control in the last four generations of selection. This indicates that there is a positive genetic correlation between 16-week body weight and frequency of leg problems. Genetic increases in 16-week body weight were accompanied by increases in egg weight and a decrease in rate of response to stimulatory lighting. The effect on fertility was inconsistent. There was no effect on hatch of fertile eggs.

Animals↗
PubMed1989

[The role of environmental and genetic factors in the development of pathology of the reproductive system in girls].

Genetic and environmental effects on reproductive development of girls are described. Possible genetic involvement is postulated in girls with opsomenorrhea, second-degree amenorrhea and juvenile bleedings. Abnormal development of the menstrual function is more commonly associated with chronic tonsillitis, stress or weight loss. Environmental effects are particularly frequent and pronounced one year before or during the menarche. Central menstrual disorders were associated with parental reproductive disorders in 47% of the cases.

Adolescent↗
PubMed2000

Long-term effect of prospective detection of high genetic risk on couples' reproductive life: data for thalassaemia.

Prospective risk detection with availability of prenatal diagnosis is the best service currently available for couples at high genetic risk Here we describe the long term effect of this service on the reproductive life of 102 couples at risk of thalassaemia, whose risk was detected prospectively by carrier screening, who made use of prenatal diagnosis, and where the woman is now over 40. Overall outcome for couples is described in terms of number of favourable versus unfavourable pregnancy outcomes. (A favourable pregnancy outcome = unaffected livebirth, or affected livebirth resulting from informed parental choice.) The 102 couples had a total of 356 pregnancies, including 302 viable pregnancies, and 88% achieved a family unburdened by thalassaemia. 68% of viable pregnancies had a favourable outcome, but only 43% of couples had only favourable outcomes, and 26% lost two or more viable wanted pregnancies. When early losses are included 58% of pregnancies had a favourable outcome, but only 30% of couples had only favourable outcomes, and 41% lost two or more pregnancies. Even with the best available service, at risk couples remain victims of chance, and a significant minority experience great difficulty in obtaining even one healthy child. Research is needed on approaches that may allow couples better control of reproductive outcomes.

Adult↗