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Review of genetics in the United States with emphasis on the prenatal, metabolic, genetic counseling, and training aspects of the field.
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A revival of interest in Haldane's equilibrium theory for X-linked lethals has been stimulated by the introduction of accurate tests for the detection of female heterozygotes in Lesch-Nyhan disease. Application of these tests appears to indicate an excess of familial cases. This excess can be attributed to ascertainment bias, a difference in female and male mutation rates, genetic drift, and reproductive compensation. Reproductive compensation will be particularly effective in increasing the proportion of familial cases if (1) birth control is widespread; (2) selection against affected males acts in utero; (3) affected sons show symptoms at an early age; and (4) sons are more highly valued than daughters. We demonstrate how only a few generations of reproductive compensation are sufficient to achieve an approximate equilibrium between selection and mutation showing a high proportion of familial cases. We also discuss the random fluctuations around equilibrium caused by genetic drift.
Over the past four decades, reproductive biotechnologies have profoundly transformed cattle breeding by accelerating genetic progress and enabling the dissemination of elite genetics. In this article, I present a perspective based on more than 40 years of practical experience in embryo technologies within Auriva-Elevage, a cooperative organization serving 30,000 farmers in southern France. The development of embryo transfer in France was closely linked to genetic and sanitary challenges, particularly the introduction of North American Holstein genetics and the restrictions on live animal imports due to infectious diseases such as Infectious Bovine Rhinotracheitis. These constraints stimulated the development of national expertise in embryo transfer. Over the years, our team has implemented and adapted a wide range of reproductive technologies including in vivo embryo production and embryo transfer, cryopreservation, embryo sexing, ovum pick-up (OPU), in vitro embryo production (IVP), embryo biopsy, genomic evaluation of embryos, and laser-assisted biopsy techniques. The genomic revolution dramatically increased the strategic value of OPU-IVP for the rapid multiplication of elite donor females. In addition to technological developments, the success of these programs has depended heavily on internal training, collaboration with national organizations such as ELIANCE (previously UNCEIA, ALLICE) and research institutes including INRAE and Toulouse veterinary school, as well as strong international exchanges through scientific networks. Practical examples such as the use of embryo biopsy to prevent genetic diseases demonstrate the applied value of these technologies in breeding programs. This review highlights the technical evolution, organizational structures, and human expertise that have shaped the implementation of reproductive biotechnologies in cattle breeding and discusses the importance of anticipating future needs to ensure continued genetic progress.
The genetic landscape of human infertility is complex with diverse etiologies. Identifying the underlying etiology is crucial for guiding reproductive decisions and improving management for infertile couples. Here, we aim to report on the molecular spectrum of monogenic genetic causes of reproductive failure. Over a 3-year period, we recruited all infertile couples considering assisted reproductive technologies (ART) for whom the underlying genetic cause had been identified, in either partner, using exome sequencing (ES). Clinical data of all participants along with their hormonal profiles, sonographic findings and spermograms were recorded. The study included 50 couples with primary infertility. Clinically, male factor infertility was documented in 26 patients, female factor infertility in 10, while reproductive failure was unexplained in the remaining 14 couples. All participating couples had potentially disease-causing variants in infertility genes. ES identified variants related to male infertility in 26 men, while variants in female infertility-related genes were detected in the remaining couples (n = 24). According to ACMG classification criteria, 78% (39/50) of couples harbored pathogenic/likely pathogenic (P/LP) variants, whereas 22% (11/50) carried variants of uncertain significance (VUS). In view of the identified genetic etiologies, the cohort was stratified into two groups based on the predicted reproductive outcome: (1) couples with significantly impaired reproductive potential, and (2) couples who can have biological children using appropriate medical interventions. However, classifications involving VUS were interpreted cautiously and considered exploratory. This study provides further evidence for the molecular heterogeneity of human infertility and highlights the usefulness of genetic testing for infertile couples pursuing ARTs.
1. Metridium senile was studied for phosphohexose-isomerase variation at three locations on Cape Cod, Massachusetts: Woods Hole, Cape Cod Canal, and Barnstable Town Boat Harbor. 2. All three locations exhibited significant polymorphism for PHI. 3. Mapping of individual polyps was performed at Barnstable to analyze spatial distributions of clones and genotypes. 4. In Barnstable, PHI does not depart significantly from Hardy-Weinberg expectations at the time of establishment of new polyps, and establishment of larvae is spatially random with respect to PHI genotype. 5. Asexual reproduction was uses as a meausre of the relative success of different PHI genotypes. There are indications that not all genotypes are equally likely to produce large clones. 6. There is significant heterogeneity among the three locations with respect to PHI genotype frequencies, suggesting that there may be geographical differentiation of the populations. 7. Sessile, asexual organisms provide powerful tools for examining the dynamic aspects of genetic structure in natural populations.
The experiences and outcomes for women identified with a BRCA1/2 pathogenic variant during young adulthood are qualitatively described but not well quantified. This study investigated the impact of BRCA1/2 status on women's reproduction, intimate partner relationships, and sexual functioning. Australian women aged 18-40 years who had predictive BRCA1/2 testing, received either a positive or negative result, and had no personal cancer history, completed an online survey that used a case-control design. Outcome measures included childbearing, use of reproductive technologies, relationship status, and sexual functioning. 579 women participated (62.0% with a BRCA1/2 PV; 38.0% without a BRCA1/2 PV). More women with a BRCA1/2 PV had children compared to those who did not (49.0% c.f., 40.5%; p = 0.045). BRCA1/2 status did not predict whether women were partnered at survey completion (Odds Ratio 1.20; 95% CI 0.80, 1.78) or their sexual functioning over the previous month (β-coefficient -0.08; 95% CI -1.15, 0.98). Women with a BRCA1/2 PV were more likely to have children after genetic testing (OR 1.83: 95% CI 1.05, 3.21) and were more likely to have a greater number of children after genetic testing (β-coefficient 0.41; 95% CI 0.10, 0.73) compared to women without a BRCA1/2 PV, after adjustment for confounders. Receiving a positive predictive BRCA1/2 result is associated with an increased likelihood of childbearing and having a greater number of children compared to receiving a negative predictive BRCA1/2 result. These findings contribute to the evidence base to inform long-term follow-up for women after predictive BRCA1/2 testing.
Reproductive function is impaired in the genetically obese (C57 B1/6J) ob/ob mouse. Serum LH, FSH, and testosterone concentrations were assessed in male ob/ob and lean littermates from 39 to 78 days of age. The lean animals demonstrated a three-fold rise in serum LH between 39 and 45 days of age that preceded a steep increase in serum testosterone which peaked at age 70 days. The obese animals did not demonstrate this LH rise; serum testosterone levels were low and had a blunted increase with age that paralleled that of normal animals. Serum FSH was lower than normal at all ages in the obese mice. The ventral prostrate and testes were small in the ob/ob mice. The castration of adult animals resulted in increased serum concentrations of both LH and FSH, with higher levels attained in the lean animals. Fifty-four-day-old castrated lean and obese mice were treated with testosterone for 15 days. Measurements of serum LH and FSH after 8 and 15 days of treatment demonstrated a marked sensitivity in the ob/ob animals to feedback inhibition of gonadotropins. This finding suggested persistent immaturity of the hypothalamic-pituitary axis in obese mice. These studies indicate that the hypogonadism of the ob/ob mouse is the result of altered hypothalamic-pituitary function.
Two reproductively isolated demes of brown trout coexist in a small Swedish mountain lake, Lake Bunnersjörna. We electrophoretically examined 102 specimens from that lake for 27 enzymes encoded by 54 loci. The two demes are fixed for different alleles at a lactate dehydrogenase locus (LDH-1); statistically significant allele frequency differences at five other loci further support the complete lack of gene flow between these demes. There are significant differences in growth rates between fish in the two demes, but no further morphological differentiation h-s been detected.--In light of these findings, the genetic distance between these populations is surprisingly small (Nei's I = 0.975). These demes represent one of the least genetically divergent, reproductively isolated sympatric pair of vertebrate populations that have been identified. The results are discussed from both an evolutionary and ecological perspective.
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We have attempted quantitatively through a series of assortative mating models to gain insight into the interaction between the usually antagonistic tendencies of artifical and natural selection pressures. We summarize some of the robust conclusions. In cases where natural selection is expressed only through the phenotype and acts in the opposite direction to the culling incline, then fixation of the dominant or recessive type can be achieved and which occurs depends critically on the initial composition of the population and the magnitude of the degree of culling compared to the selection coefficients. With traits determined at two loci in the case that the double heterozygote is the desired kind, the effect of selfing can only be overcome by very strong artificial selection pressures (high culling order). The degree of culling to achieve its objective can be relaxed with weakening of linkage. The relevant comparison is r2+(1-r)2less than 2(1-c) indicating the precise extent of culling needed, to prevent fixation. The relationships are more complex when natural selection forces are also involved (see Model IV).
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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.
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.