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The evolutionary biology and population genetics underlying fungal strain typing.

Strain typing of medically important fungi and fungal population genetics have been stimulated by new methods of tapping DNA variation. The aim of this contribution is to show how awareness of fungal population genetics can increase the utility of strain typing to better serve the interests of medical mycology. Knowing two basic features of fungal population biology, the mode of reproduction and genetic differentiation or isolation, can give medical mycologists information about the intraspecific groups that are worth identifying and the number and type of markers that would be needed to do so. The same evolutionary information can be just as valuable for the selection of fungi for development and testing of pharmaceuticals or vaccines. The many methods of analyzing DNA variation are evaluated in light of the need for polymorphic loci that are well characterized, simple, independent, and stable. Traditional population genetic and new phylogenetic methods for analyzing mode of reproduction, genetic differentiation, and isolation are reviewed. Strain typing and population genetic reports are examined for six medically important species: Coccidioides immitis, Histoplasma capsulatum, Candida albicans, Cryptococcus neoformans, Aspergillus fumigatus, and A. flavus. Research opportunities in the areas of genomics, correlation of clinical variation with genetic variation, amount of recombination, and standardization of approach are suggested.

Biological Evolution↗

Reproductive mode and population genetic structure of the cereal aphid Sitobion avenae studied using phenotypic and microsatellite markers.

As French populations of the aphid Sitobion avenae exhibit a range of reproductive modes, this species provides a good opportunity for studying the evolution of breeding system variation. The present analysis combined ecological and genetic investigations into the spatial distribution of variation in reproductive mode. Reproductive mode was characterized in 277 lineages of S. avenae from France, and these aphids were scored for five microsatellite loci. The analyses revealed strong geographical partitioning of breeding systems, with obligate asexuals mostly restricted to the south of France, while lineages producing sexual forms were more common in the north. Contrary to what might be anticipated for organisms with frequent parthenogenesis, there was substantial genic and genotypic diversity, even in the obligately asexual lineages. More than 120 different genotypes were detected among the 277 aphid lineages, with an average of 5.9 alleles per locus (range four to 16) and heterozygosity of 56.7%. As with previous studies of allozyme variation in aphids, most loci showed heterozygote deficits, and disequilibrium was common among allelic variants at different loci, even after removal of replicate copies of genotypes that might have been derived through clonal reproduction. Our results suggest that selection is important in structuring reproductive systems and genetic variation in French S. avenae. Canonical correspondence analysis was employed to examine the associations between genotypic and phenotypic variables, enabling the identification of alleles correlated with life-history traits.

Animals↗

[Genetic engineering and assisted reproduction techniques in man: a framework for sociologic analysis].

The possibilities opened up by genetic engineering and assisted reproduction techniques require reflection by sociologists and extensive public debate. In view of their potential as factors of social change, evaluation and control are warranted. They can be viable only if transparent and through public co-responsibility, for which an exchange of views is needed between all those who play a part in the development of said techniques. This dialogue must be wholly interdisciplinary and democratic.

Forecasting↗

Passing it on: should health care professionals be permitted to disclose patients' genetic information to their reproductive partners?

This article considers whether Australian law should permit health care professionals to disclose patients' genetic information to their reproductive partners without the patients' consent. The issue is addressed with reference to four genetic disorders (Huntington Disease, Familial Adenomatous Polyposis, Multiple Endocrine Neoplasia Type 2A and Cystic Fibrosis) which illustrate differences in inheritance traits and availability of effective treatments. The article explores the familial nature of these disorders and the notion that genetic information has implications which extend beyond the individual patient to third parties such as reproductive partners. It addresses the opinions of legal academics and regulatory bodies regarding the potential amendment of Australian laws to permit such disclosure. Ultimately, it is submitted that the application of current laws regarding medical information to the needs of genetics is unlikely to generate adequate results. To allow for a more appropriate response to this debate, health care professionals' duties to patients should be qualified when it concerns reproductive partners.

Adenomatous Polyposis Coli↗

Evolution of egg dumping in a subsocial insect.

Egg dumping, or abandonment of eggs and young to the care of other conspecifics, frees individuals from costs of maternal care while potentially imposing energetic and ecological costs on egg recipients. It is not clear, however, that egg dumping necessarily represents selfish manipulation of egg recipients, and in some ecological contexts, recipients may benefit from enlarged broods. Thus, egg dumping may either be mutually beneficial for dumpers and recipients or entail costs for dumpers that are compensated by other means, such as improving reproduction of genetically related egg recipients. Here I use field experiments to test the relative importance of manipulation (i.e., "parasitism"), mutualism, and kin selection in the evolution of egg dumping in the tingid lace bug Gargaphia solani. In support of mutualism and kin selection, I found that reproduction of egg recipient G. solani benefits from brood enlargement, most likely because eggs and gregarious nymphs find safety in greater numbers. But contrary to both parasitism and mutualism, egg dumper reproduction was not improved by offspring abandonment. Indeed, dumpers laid smaller clutches than recipients, and dumpers did not convert a survival advantage into greater future reproduction. Genetic analyses of a natural G. solani population revealed, however, that dumpers are related to their egg recipients. Moreover, Hamilton's rule showed that egg-dumping G. solani earn sufficient indirect genetic benefits for kin selection to favor the behavior. Thus, egg dumping in some species may be kin-selected cooperation rather than parasitism or mutualism.

Animals↗

Genetic basis of human reproductive endocrine disorders.

Disturbed human reproductive function may be caused by environmental and/or genetic factors. Much information related to single gene defects underlying reproductive failure has become available in recent years due to advances in molecular biology. In this review, techniques currently applied for deoxyribonucleic acid (DNA) analysis are addressed. We also highlight underlying molecular mechanisms and the corresponding clinical presentation of single gene defects affecting (i) the hypothalamic-pituitary-gonadal axis, resulting in disturbed gonadotrophin-releasing hormone (GnRH) neuron migration, or leading to defective gonadotrophins, gonadotrophin receptors and the Gs alpha protein; (ii) gonadal and adrenal steroid biosynthesis and (iii) steroid and insulin receptors. The potential genetic basis of polycystic ovary syndrome is also discussed. Although disease states caused by well-defined genetic abnormalities appear to represent only a small proportion of those found in the patient population, it should be considered that these affected individuals represent only the most severe cases in a wide spectrum of genetic abnormalities underlying disturbed fertility. Comprehension of these extreme cases will provide the basis for the elucidation of more common reproductive disorders as the result of subtle genetic changes or increased susceptibility to environmental factors.

Endocrine System Diseases↗

Genetic mating systems and reproductive natural histories of fishes: lessons for ecology and evolution.

Fish species have diverse breeding behaviors that make them valuable for testing theories on genetic mating systems and reproductive tactics. Here we review genetic appraisals of paternity and maternity in wild fish populations. Behavioral phenomena quantified by genetic markers in various species include patterns of multiple mating by both sexes; frequent cuckoldry by males and rare cuckoldry by females in nest-tending species; additional routes to surrogate parentage via nest piracy and egg-thievery; egg mimicry by nest-tending males; brood parasitism by helper males in cooperative breeders; clutch mixing in oral brooders; kinship in schooling fry of broadcast spawners; sperm storage by dams in female-pregnant species; and sex-role reversal, polyandry, and strong sexual selection on females in some male-pregnant species. Additional phenomena addressed by genetic parentage analyses in fishes include clustered mutations, filial cannibalism, and local population size. All results are discussed in the context of relevant behavioral and evolutionary theory.

Animals↗

Genetic approaches to unraveling reproductive disorders: examples of bedside to bench research in the genomic era.

Despite the rapid advances in medical genetics, many clinicians and investigators remain unaware of the general approaches that can be used to map genes. Although there are specific challenges to using genetic approaches in reproductive medicine, the following report summarizes mapping efforts for three diseases: adrenal hypoplasia congenita, hypergonadotropic ovarian failure, and polycystic ovary syndrome. The themes of rare and novel phenotypes, genetically homogenous populations, and genotype/phenotype correlations are emphasized.

DAX-1 Orphan Nuclear Receptor↗

Identification of genetic regions of importance for reproductive performance in female mice.

Both environmental and genetic factors can dramatically affect reproductive performance in mice. In this study we have focused on the identification of genetic regions, quantitative trait loci (QTL), which affect the breeding capacity of female mice. We have identified polymorphic microsatellite markers for the mouse strains used and performed a genomewide scan on 237 females from a gene-segregating backcross between a high breeder and a relatively poor breeder. The high-breeder mouse strain we used is the inbred NFR/N mouse (MHC haplotype H-2q), which has extraordinary good breeding properties. The moderate breeder chosen for F(1) and N2 progeny was B10.Q, which is a genetically well-characterized MHC-congenic mouse of the H-2q haplotype. Each of the 237 females of the N2 generation was allowed to mate twice with MHC-congenic B10.RIII (H-2r) males and twice with B10.Q males. A predetermined number of phenotypes related to reproductive performance were recorded, and these included litter size, neonatal growth, and pregnancy rate. Loci controlling litter size were detected on chromosomes 1 (Fecq3) and 9 (Fecq4). The neonatal growth phenotype was affected by Fecq3 and a locus on chromosome 9 (Neogq1). On chromosome 11 two loci affecting the pregnancy rate (Pregq1 and Pregq2) were identified. Furthermore, on chromosomes 13 and 17 we found loci (Pregq3 and Pregq4) influencing the outcome of allogeneic pregnancy (allogeneic by means of MHC disparity between mother and fetuses). A locus on chromosome 1 affecting maternal body weight was also identified and has been denoted Bwq7. It is well known that reproductive performance is polygenically controlled, and the identification of the major loci in this complex process opens the possibility of investigating the natural genetic control of reproduction.

Animals↗