Estimating genome-wide heterozygosity: effects of demographic history and marker type.

Heterozygosity-fitness correlations (HFCs) are often used to link individual genetic variation to differences in fitness. However, most studies examining HFCs find weak or no correlations. Here, we derive broad theoretical predictions about how many loci are needed to adequately measure genomic heterozygosity assuming different levels of identity disequilibrium (ID), a proxy for inbreeding. We then evaluate the expected ability to detect HFCs using an empirical data set of 200 microsatellites and 412 single nucleotide polymorphisms (SNPs) genotyped in two populations of bighorn sheep (Ovis canadensis), with different demographic histories. In both populations, heterozygosity was significantly correlated across marker types, although the strength of the correlation was weaker in a native population compared with one founded via translocation and later supplemented with additional individuals. Despite being bi-allelic, SNPs had similar correlations to genome-wide heterozygosity as microsatellites in both populations. For both marker types, this association became stronger and less variable as more markers were considered. Both populations had significant levels of ID; however, estimates were an order of magnitude lower in the native population. As with heterozygosity, SNPs performed similarly to microsatellites, and precision and accuracy of the estimates of ID increased as more loci were considered. Although dependent on the demographic history of the population considered, these results illustrate that genome-wide heterozygosity, and therefore HFCs, are best measured by a large number of markers, a feat now more realistically accomplished with SNPs than microsatellites.

QTL mapping for sexually dimorphic fitness-related traits in wild bighorn sheep.

Dissecting the genetic architecture of fitness-related traits in wild populations is key to understanding evolution and the mechanisms maintaining adaptive genetic variation. We took advantage of a recently developed genetic linkage map and phenotypic information from wild pedigreed individuals from Ram Mountain, Alberta, Canada, to study the genetic architecture of ecologically important traits (horn volume, length, base circumference and body mass) in bighorn sheep. In addition to estimating sex-specific and cross-sex quantitative genetic parameters, we tested for the presence of quantitative trait loci (QTLs), colocalization of QTLs between bighorn sheep and domestic sheep, and sex × QTL interactions. All traits showed significant additive genetic variance and genetic correlations tended to be positive. Linkage analysis based on 241 microsatellite loci typed in 310 pedigreed animals resulted in no significant and five suggestive QTLs (four for horn dimension on chromosomes 1, 18 and 23, and one for body mass on chromosome 26) using genome-wide significance thresholds (Logarithm of odds (LOD) >3.31 and >1.88, respectively). We also confirmed the presence of a horn dimension QTL in bighorn sheep at the only position known to contain a similar QTL in domestic sheep (on chromosome 10 near the horns locus; nominal P<0.01) and highlighted a number of regions potentially containing weight-related QTLs in both species. As expected for sexually dimorphic traits involved in male-male combat, loci with sex-specific effects were detected. This study lays the foundation for future work on adaptive genetic variation and the evolutionary dynamics of sexually dimorphic traits in bighorn sheep.

[Work characteristics and health of correctional officers]. / Les caractéristiques du travail et la santé des agents en services de détention.

BACKGROUND: The association between the psychosocial work environment and mental health problems has been well documented over the past years. Karasek and Theorell's job strain model and Siegrist's effort/reward imbalance model have been associated to several physical and mental health problems. Moreover, in the last decade, the Quebec correctional services sector has known an important increase in sickness benefit claims for mental health problems. This study aimed to describe the psychosocial work characteristics and health of Quebec correctional officers and to determine the occupational risk factors associated to psychological distress among them. METHODS: This cross-sectional study was realized among 1034 correctional officers from 18 prisons in the province of Quebec, 668 men and 366 women. The response rate was 76%. Psychological demands, decision latitude, social support at work, reward, and psychological distress have been documented by telephone interviews during spring 2000. RESULTS: Correctional officers were more exposed to adverse psychosocial factors at work than a comparable sample of Quebec workers and they reported more health problems. Results showed that the same sources of psychological distress affected men and women, but sometimes at different degrees. High psychological demands combined with low or high decision latitude, and effort/reward imbalance were associated to psychological distress independently of potential confounding factors. Among other work factors associated to the report of high psychological distress among correctional officers were low social support at work, and conflicts with colleagues and superiors. CONCLUSION: Many adverse psychosocial factors at work were in excess among correctional officers compared to workers from the general population. These factors, also related to high levels of psychological distress, could be addressed with the goal of primary prevention of mental health problems at work.

Reproductive health and work: different experiences.

Quebec and Denmark passed legislation in 1981 that aims to protect pregnant women and their unborn children from health hazards in the workplace. Finland passed similar legislation in 1991. While these measures have much in common, they are applied in very different ways. Approximately 1% of pregnant working women benefit from a "special maternity leave" in Denmark, compared with 0.1% in Finland, while in Quebec, nearly 40% of working women benefit from preventive reassignment measures during their pregnancies. In this article, we will analyze the reasons for these disparities between rates of utilization in Finland, Denmark, and Quebec in light of the Quebec experience over the last 16 years.

[The professional life and the health of nurses since the transformation of the Québec health system.]. / La vie professionnelle et la santé des infirmières depuis la transformation du réseau de la santé

Over the last years, the Quebec health system has gone through a period of transformation aimed at cost reduction and better efficiency. The present study describes the effects of the transformation on the professional life and on the health of nurses in the Quebec City urban area. Despite a cross-sectional study not allowing links from cause to effect and despite the fact that the study only includes nurses who were still employed by institutions, the research shows an increase of the prevalence of a higher level of psychological distress in nurses since the beginning of the transformation. Interventions in the work place should be geared to professional factors that nurses identify as problematical.