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Practicalities of genetic studies in human stroke.

Considerable evidence suggests genetic factors are important in the pathogenesis of multifactorial stroke. However, studies identifying the underlying genes have been largely disappointing. This chapter reviews the different approaches and their relative merits. It is likely stroke is a polygenic disorder and that underlying genes may interact within environmental risk factors. Stroke itself is a syndrome caused by a number of different pathologies, which may result from different genetic predispositions. Therefore accurate stroke subtyping is likely to be important in identifying genetic associations. Previous studies have suffered from small sample size, lack of adequate phenotyping, and poor case-control matching. The most popular approach to identifying genes in human polygenic ischemic stroke has been the candidate gene approach. The relative merits of this approach are discussed. More recently this has been extended to family-based association studies. Linkage-based approaches have been used less although current studies are implementing the affected-sibling-pair method. In the future genome-wide association studies are likely to become more widely used.

Case-Control Studies↗

SAGE programs: model-free linkage analysis for complex cardiovascular phenotypes.

A complex disease trait refers to a phenotype that does not follow simple Mendelian segregation attributable to a single gene locus, but instead may be caused by multiple disease loci, their interactions, polygenic inheritance, and environmental effects. Most cardiovascular disorders are thought to have a polygenic basis with complex interactions with environmental factors. A gene that increases or decreases the risk to a complex cardiovascular disease (susceptibility gene) can now be mapped to a specific chromosomal region by model-free linkage analysis, and follow-up molecular genetic studies can identify the specific gene at the locus. This chapter describes a protocol for model-free linkage analysis of a complex trait, as implemented in the popular genetic analysis software-SAGE. In particular, the Haseman-Elston sib-pair regression method is introduced and implemented with examples to demonstrate how to identify susceptibility loci for complex traits.

Cardiovascular Diseases↗

The oxidative processes induced in cell suspensions of Solanum species by culture filtrate of Phytophthora infestans.

Solanum genotypes that differ in the level of polygenic resistance to the oomycete plant pathogen Phytophthora infestans were studied for their oxidative response to culture filtrate (CF) of the pathogen. Reactive oxygen species (ROS) production, peroxidase activity and lipid peroxidation have been studied in the CF-treated cell suspensions derived from leaves of the resistant S. nigrum (nonhost) and S. tuberosum cv. Bzura as well as from the susceptible S. tuberosum cv. Tarpan and clone H-8105. In both the resistant and susceptible cells the CF induced similar processes, but these varied with respect to the kinetics and intensity. In all cells probably the membrane-bound NADPH oxidase, was responsible for the ROS production. This process was more intensive and prolonged in the susceptible cells than in the resistant ones. The CF treatment slightly affected peroxidase activity in all cells studied. Lipid peroxidation that occurred as a consequence of the ROS accumulation was pronounced mainly in the susceptible cells. We suggest that lack of stringent control of the oxidative processes and sensitivity to the pathogen toxins may be decisive for limited polygenic resistance in potato.

Cells, Cultured↗

Genomic characterization of Alzheimer's disease and genotype-related phenotypic analysis of biological markers in dementia.

More than 180 genes distributed across the human genome are potentially involved in the pathogenesis of Alzheimer's disease (AD). The AD population shows a higher genetic variation rate than the control population. Significant differences in allelic distribution and frequency exist when AD-related polygenic clusters are compared with other forms of dementia, indicating that the genetic component in neurodegenerative dementia differs from that of other CNS disorders. The characterization of AD genotype-related phenotypic profiles reveals substantial differences in biological markers among AD clusters associated with different genes and/or allelic combinations. AD and dementia with vascular component (DVC) are the most prevalent forms of dementia. Both clinical entities share many similarities, but they differ in their major phenotypic and genotypic profiles, as revealed by structural and functional genomics studies. Comparative phenotypic studies have identified significant differences in 25% of more than 100 parametric variables, including anthropometric values, cardiovascular function, blood pressure, lipid metabolism, uric acid metabolism, peripheral calcium homeostasis, liver function, alkaline phosphatase, lactate dehydrogenase, red and white blood cells, regional brain atrophy, and brain blood flow velocity. Functional genomic studies incorporating apolipoprotein E (APOE)-related changes in biological markers extended the difference between AD and DVC by up to 57%. Structural genomic studies with AD-related genes, including APP, MAPT, APOE, PS1, PS2, A2M, ACE, AGT, cFOS, and PRNP, demonstrate different genetic profiles in AD and DVC, with an absolute genetic variation rate in the range of 30-80%, depending upon genes and genetic clusters. The relative polymorphic variation in genetic clusters integrated by two, three or four genes associated with AD ranges from 1 to 3%. The main phenotypic differences in AD are genotype dependent, indicating a powerful influence of polygenic factors on the AD phenotypic profile. All these genotypic and phenotypic variations bring about important consequences for the pharmacogenomics of AD.

Adolescent↗

Large-scale gene expression differences across brain regions and inbred strains correlate with a behavioral phenotype.

Behaviors are often highly heritable, polygenic traits. To investigate molecular mediators of behavior, we analyzed gene expression patterns across seven brain regions (amygdala, basal ganglia, cerebellum, frontal cortex, hippocampus, cingulate cortex, and olfactory bulb) of 10 different inbred mouse strains (129S1/SvImJ, A/J, AKR/J, BALB/cByJ, BTBR T+ tf/J, C3H/HeJ, C57BL/6J, C57L/J, DBA/2J, and FVB/NJ). Extensive variation was observed across both strain and brain region. These data provide potential transcriptional intermediates linking polygenic variation to differences in behavior. For example, mice from different strains had variable performance on the rotarod task, which correlated with the expression of >2000 transcripts in the cerebellum. Correlation with this task was also found in the amygdala and hippocampus, but not in other regions examined, indicating the potential complexity of motor coordination. Thus we can begin to identify expression profiles contributing to behavioral phenotypes through variation in gene expression.

Amygdala↗

Identifying genetic determinants in human essential hypertension.

Genetic factors play an important role in the pathophysiology of human essential hypertension. The remarkable success of molecular genetic techniques in identifying the basis for single gene disorders at the DNA level has encouraged investigators to apply similar techniques in an attempt to identify blood pressure genes. In contrast to single gene disorders, however, the study of blood pressure is complicated by its quantitative, complex, heterogeneous, and polygenic nature. This article examines current methods and strategies for identifying genetic determinants in human hypertension. The availability of highly polymorphic markers, the advances in quantitative trait analysis, and the mapping of blood pressure-determining genes in a polygenic rat model of hypertension suggest that molecular genetic research in human hypertension has come of age.

Animals↗

Spatially Contextualized Integrative Genomics Highlights Neuronal and Glial Regulatory Programs in Low Back Pain.

PURPOSE: Low back pain (LBP) is a heterogeneous pain condition with a measurable genetic contribution, but the genes, brain cell types, and spatial tissue contexts through which inherited risk is expressed remain unclear. We aimed to define cell-type-specific and spatially contextualized genetic mechanisms underlying LBP. METHODS: FinnGen R12 LBP GWAS summary statistics (42,521 cases and 353,224 controls) were integrated with brain single-nuclei eQTL data across eight major brain cell classes. We evaluated genome-wide polygenic signal using LDSC, prioritized genes using MAGMA and PoPS, and performed brain cell-type-specific eQTL-anchored Mendelian randomization, primarily based on single-instrument Wald ratio estimates, followed by Bayesian colocalization. Spatial genetic mapping was conducted using gsMap in an E16.5 murine embryonic atlas and two adult human lumbar spinal cord Visium sections. Selected candidates were assessed by RT-qPCR in neuronal-like and astroglial-like inflammatory cell models. RESULTS: LDSC supported interpretable polygenic signal for LBP. MAGMA and PoPS showed partial gene-level convergence, with TCF4 and TMEFF2 supported by both approaches. Across 1641 tested gene-cell type exposures, significant eQTL-anchored MR associations were concentrated in excitatory neurons, oligodendrocytes, inhibitory neurons, and astrocytes. Integrated eQTL-anchored MR, colocalization, and gene-prioritization evidence highlighted CLEC18A, QPRT, and GMPPB as higher-priority non-MHC candidates with moderate, but not strong, colocalization support. gsMap localized LBP-associated enrichment to neuroaxis-related embryonic regions, including brain, spinal cord, sympathetic nerve, and dorsal root ganglion, and to neuronal-like niches in adult lumbar spinal cord. RT-qPCR showed model-dependent expression changes, with QPRT and LGI4 preferentially responsive in neuronal-like SH-SY5Y cells and GMPPB and DPYSL5 responsive in astroglial-like U251 cells. CONCLUSION: These findings support neuronal and glial regulatory programs as plausible contributors to LBP genetic susceptibility and highlight CLEC18A, QPRT, and GMPPB as higher-priority non-MHC candidates with moderate colocalization support. The results provide a spatially contextualized framework for candidate prioritization in LBP, while emphasizing the need for larger cell-type-specific eQTL resources and functional validation before therapeutic or mechanistic conclusions can be drawn.

Mendelian randomization↗

Genetics of obesity.

Obesity is a typical common multifactorial disease in which environmental and genetic factors interact. In rare cases of severe obesity with childhood onset, a single gene has a major effect in determining the occurrence of obesity, with the environment having only a permissive role in the severity of the phenotype. Exceptional mutations of the leptin gene and its receptor, pro-opiomelanocortine (POMC), prohormone convertase 1 (PC1) and more frequently, mutations in the melanocortin receptor 4 (1 to 4% of very obese cases) have been described. All these obesity genes encode proteins that are strongly connected as part of the same loop of the regulation of food intake. They all involve the leptin axis and one of its hypothalamic targets; the melanocortin pathway. Pathways of bodyweight regulation involved in monogenic forms of obesity might represent targets for future drug development. Successful leptin protein replacement in a leptin-deficient child has contributed to the validation of the usefulness of gene screening in humans. However, the individual variability in response to leptin treatment might be related to genetic variability. The efficiency of leptin itself or of small-molecule agonists of the leptin receptor should be studied in relation with genetic variations in the leptin gene promoter. The most common forms of obesity are polygenic. Two general approaches have been used to date in the search for genes underlying common polygenic obesity in humans. The first approach focuses on selected genes having some plausible role in obesity on the basis of their known or presumed biological role. This approach yielded putative susceptibility genes with only small or uncertain effects. The second approach attempts to map genes purely by position and requires no presumptions on the function of genes. Genome-wide scans identify chromosomal regions showing linkage with obesity in large collections of nuclear families. Genome-wide scans in different ethnic populations have localized major obesity loci on chromosomes 2, 5, 10, 11 and 20. Susceptibility gene(s) for obesity may be positionally cloned in the intervals of linkage. The candidate gene and positional cloning of major obesity-linked regions approaches are discussed in this paper.

Genetic Linkage↗

The Continuity Trap in Data Science Health Research.

Secondary use is now the ordinary condition of data science health research rather than an exception to it. Electronic health records collected for clinical care become prediction tools and inputs for generative AI; imaging archives become foundation-model corpora; genomic datasets become resources for polygenic risk scores; and legacy biospecimens become renewable, indefinitely distributable cell lines. Governance has responded by emphasizing verifiable instruments such as provenance logs, repository approvals, broad-consent forms, data-use agreements, model cards, records of processing, and locality-preserving architectures. These instruments are necessary, and they answer real questions about lineage, privacy, institutional responsibility, and accountability, but they are not sufficient to establish that a present use remains ethically justified. We define ethical continuity as the persistence of normatively relevant relationships between the original conditions of data generation or material collection and subsequent downstream uses, such that current uses remain justifiable in light of the expectations, permissions, meanings, and relational obligations present at entrustment. We then define the Continuity Trap as a review-stage governance error in which a salient signal of continuity in one domain is treated as sufficient evidence of ethical continuity overall, causing inquiry into the remaining domains to close prematurely. The trap is not ordinary noncompliance, ethics creep, or a demand for universal rereview; it is a cross-domain inference error that can arise even in careful, good-faith review. We distinguish it from proxy closure, of which it is a continuity-specific subtype, and from Goodhart's and Campbell's laws, which describe how measures degrade once they become targets. We operationalize ethical continuity across 4 domains: provenance, semantics, authorization, and relational standing, developed in our Representational Veracity framework, and we show that these domains can diverge as data are linked, transformed, modeled, and redeployed. We identify the institutional mechanisms-provenance privilege, descriptor sedimentation, authorization fossilization, and community effacement-that cause auditable signals to be overread, and we examine how the US Health Insurance Portability and Accountability Act (HIPAA) of 1996, the General Data Protection Regulation, the European Health Data Space, US Food and Drug Administration guidance, the US National Institute of Standards and Technology (NIST) AI Risk Management Framework, and federated-learning governance can reduce risk while still inducing continuity traps. We apply the framework to consent and nonconsent settings, including public health, immunization, syndromic, and wastewater surveillance, polygenic risk scores, induced pluripotent stem cells, federated learning, and health-related large language models. The policy implication is trigger-based continuity review: rather than rereviewing every reuse, investigators and reviewers should identify the weakest continuity domain at the present data stage and impose a domain-matched safeguard, recorded in a short continuity statement. This reframing is intended for the committees, repositories, funders, and governance bodies that decide whether reuse may proceed, and it matters most in cross-border and low-resource settings. Provenance should begin ethical review; it should not end it.

Data Science↗

Combined association and linkage analysis for general pedigrees and genetic models.

A combined score test for association and linkage analysis is introduced, based on a biologically plausible model with association between markers and causal genes and penetrance between phenotypes and the causal gene. The test is based on a retrospective likelihood of marker data given phenotypes, treating the alleles of the causal gene as hidden data. It is defined for arbitrary outbred pedigrees, a wide class of genetic models including polygenic and shared environmental effects and allows for missing marker data. It is multipoint, taking marker genotypes from several loci into account simultaneously. The score vector has one association and one linkage component, which can be used to define separate tests for association and linkage. For complete marker data, we give closed form expressions for the efficiency of the linkage, association and combined tests. These are examplified for binary and quantitative phenotypes with or without polygenic effects. The conclusion is that association tests are comparatively more efficient than linkage tests for strong association, weak penetrance models, small families and non-extreme phenotypes, whereas the linkage test is more efficient for weak association, strong penetrance models, large families and extreme phenotypes. The combined test is a robust alternative, which never performs much worse than the best of the linkage and association tests, and sometimes significantly better than both of them. It should be particularly useful when little is known about the genetic model.

Journal Article↗

NIDDM genes in mice: deleterious synergism by both parental genomes contributes to diabetogenic thresholds.

We used mouse genetics to model how polygenic thresholds for the transition from impaired glucose tolerance (IGT) to NIDDM are reached. NON/Lt and NZO/Hl are inbred mouse strains selected for IGT and polygenic obesity, respectively. Their F1 male progeny consistently developed NIDDM. Genetic analysis of F2 males from both cross directions identified an NON-derived diabetogenic locus, Nidd 1, on chromosome (Chr) 4 near the leptin receptor. This locus was associated with reduced plasma insulin, increased non-fasted blood glucose, and lower body weight. Another NON-derived diabetogenic locus on Chr 18 (Nidd2) that controls blood glucose was identified. An NZO-derived diabetogenic region on Chr 11 (Nidd3), possibly comprising two separate loci, reduced ability to sustain elevated plasma insulin and significantly reduced weight gain over time. Thus, the diabetogenic synergism between genetic loci from strains separately exhibiting subthreshold defects perturbing glucose homeostasis underscores the likely complexity of the inheritance of obesity-associated forms of NIDDM in humans.

Animals↗

Genetic analysis of late-onset type 2 diabetes in a mouse model of human complex trait.

Type 2 diabetes is a complex trait with both genes and environmental factors contributing to susceptibility. Except for rare subtypes with monogenic inheritance, the genetic basis of type 2 diabetes is unknown because of the complex and heterogeneous nature of the disease. By using the NSY mouse, an inbred mouse model of type 2 diabetes, we genetically dissected late-onset type 2 diabetes and demonstrated age-dependent changes in the genetic control of type 2 diabetes as well as polygenic inheritance. Three major loci (Nidd1nsy, Nidd2nsy, Nidd3nsy) were mapped on mouse chromosomes (Chr) 11, 14, and 6, respectively. The existence of a fourth locus (Nidd4nsy) with an age-dependent effect was suggested by longitudinal, but not cross-sectional, analysis of linkage data. Nidd1nsy and Nidd4nsy appear to affect insulin secretion, whereas Nidd2nsy and Nidd3nsy appear to affect insulin sensitivity. A locus on Chr 6 was significantly linked to epididymal fat weight. A candidate disease gene (Tcf2) on Chr 11, encoding hepatic nuclear factor-1beta, was shown to have a rare sequence variant in the DNA binding domain in the model. The mouse model we used will serve as a useful model for future studies on the etiology of late-onset polygenic type 2 diabetes in humans.

Adipose Tissue↗

Identification of epistatic interaction involved in obesity using the KK/Ta mouse as a Type 2 diabetes model: is Zn-alpha2 glycoprotein-1 a candidate gene for obesity?

The KK/Ta strain serves as a suitable polygenic mouse model for the common form of type 2 diabetes associated with obesity in humans. Recently, we reported the susceptibility loci contributing to type 2 diabetes and related phenotypes in KK/Ta mice. In this study, we focused on expression in the kidneys and liver of KK/Ta and BALB/c mice using differential display (DD) PCR. Zn-alpha(2) glycoprotein-1 (Azgp1) mRNA levels were increased in the kidneys and liver in KK/Ta mice, and sequence analysis revealed a missense mutation. We analyzed the relationship between this polymorphism and various phenotypes in 208 KK/Ta x (BALB/c x KK/Ta) F1 backcross mice. Statistical analysis revealed that Azgp1 and D17Mit218 exhibit a suggestive linkage to body weight (8 weeks) (logarithm of odds 2.3 and 2.9, respectively). Moderate gene-gene interactions were observed at these loci. Adiponectin mRNA levels in 3T3-L1 cells transfected with the expression pcDNA 3.1 vector containing Azgp1 coding sequence of KK/Ta mice were significantly higher than those of BALB/c mice. These results suggest that Azgp1 is a possible candidate gene for regulation of body weight, elucidation of polygenic inheritance, and age-dependent changes in the genetic control of obesity.

Adiponectin↗

Emerging epidemic of type 2 diabetes in youth.

This review considers the epidemiologic evidence of an increasing incidence of type 2 diabetes in youth, the classification and diagnostic issues related to diabetes in young populations, pathophysiologic mechanisms relevant to the increasing incidence, the role of genetics and environment, and the community challenge for prevention and treatment. Type 2 diabetes in youth has been recognized to be frequent in populations of native North Americans and to comprise some 30 percent of new cases of diabetes in the 2nd decade of life, largely accounted for by minority populations and associated with obesity. Among Japanese schoolchildren, type 2 diabetes is seven times more common than type 1, and its incidence has increased more than 30-fold over the past 20 years, concomitant with changing food patterns and increasing obesity rates. The forms of diabetes seen in children and youth include typical type 1, occurring in all races; type 2, seen predominantly in minority youth; atypical diabetes, seen as an autosomal dominantly transmitted disorder in African-American populations; and maturity-onset diabetes of the young (MODY), seen rarely and only in Caucasians. Of the nonautoimmune forms of diabetes seen in youth, only type 2 diabetes is increasing in incidence. Proper classification requires consideration of onset (acute/severe versus insidious), ethnicity, family history, presence of obesity, and if necessary, studies of diabetes related autoimmunity. Insulin resistance predicts the development of diabetes in Pima Indians, in offspring of parents with type 2 diabetes, and in other high-risk populations. African-American children and youth have greater insulin responses during glucose tolerance testing and during hyperglycemic clamp study than do whites. There is also evidence of altered beta-cell function preceding the development of hyperglycemia. Of particular interest is the evidence that abnormal fetal and infantile nutrition is associated with the development of type 2 diabetes in adulthood. The thrifty phenotype hypothesis states that poor nutrition in fetal and infant life is detrimental to the development and function of the beta-cells and insulin sensitive tissues, leading to insulin resistance under the stress of obesity. The thrifty genotype hypothesis proposes that defective insulin action in utero results in decreased fetal growth as a conservation mechanism, but at the cost of obesity-induced diabetes in later childhood or adulthood. The vast majority of type 2 diabetes in adults is polygenic and associated with obesity. Monogenic forms (MODY, maternally transmitted mitochondrial mutations) are rare, but are more likely to appear in childhood. Linkage studies of the common polygenic type 2 diabetes have emphasized the heterogeneity of the disorder. The prevention and treatment of type 2 diabetes in children and youth is a daunting challenge because of the enormous behavioral influence, difficulty in reversing obesity, and typical nonadherence in this age-group. The emerging epidemic of type 2 diabetes in the pediatric population, especially among minorities whose proportion in the U.S. population is increasing, presents a serious public health problem. The full effect of this epidemic will be felt as these children become adults and develop the long-term complications of diabetes.

Adolescent↗

Clinical description and mode of inheritance of idiopathic epilepsy in English springer spaniels.

OBJECTIVE: To determine clinical characteristics and mode of inheritance of idiopathic epilepsy (IE) in English Springer Spaniels. DESIGN: Original study. ANIMALS: 45 dogs with IE and 74 siblings and their respective parents. PROCEDURE: IE was diagnosed on the basis of age at the time of seizure onset and results of laboratory testing and neurologic examinations. Simple segregation analysis was performed with the Davie method. RESULTS: Median age at the onset of seizures was 3 years; however, 9 (20%) dogs were between 5 and 6 years old at the time of the onset of seizures. Twenty-one dogs (47%) had generalized seizures, and 24 (53%) had focal onset seizures. Results of segregation analysis were consistent with partially penetrant autosomal recessive or polygenic inheritance. Simulated linkage indicated that there was a 58% chance of obtaining suggestive linkage with the available pedigrees. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggest that in English Springer Spaniels, IE segregates in a manner that is consistent with partially penetrant autosomal recessive inheritance (ie, a single major locus with modifying genes) or polygenic inheritance. Given enough families with accurate phenotypic information and available DNA, it should be possible to use genetic linkage analysis to identify chromosomal segments containing the causative gene or genes.

Age Factors↗

Estimation of effects of single genes on quantitative traits.

Studies involving the effects of single genes on quantitative traits may involve closed populations, selection may be practiced, and the quantitative trait of concern may also be influenced by background genes that are inherited in a polygenic manner. It is shown analytically that analysis of such data by ordinary least squares, the usual method of analysis, can lead to finding an excess of spurious significant effects of single genes, when no effect exists, for both randomly and directionally selected populations and can lead to bias in estimates of single-gene effects when selection has been practiced. The bias depends on heritability of the polygenic effects on the trait, selection intensity, mode of inheritance, magnitude of gene effect, gene frequency, and data structure. It is argued that when genotypes of individuals can be identified for all individuals with observations on the trait, use of mixed-model procedures under an animal model treating single-gene effects as fixed effects can provide unbiased estimates of single-gene effects and exact tests of associated hypotheses for pedigreed populations, even when selection is practiced. Results are illustrated through computer simulation.

Animals↗

Challenges and opportunities for integrating genetically modified animals into traditional animal breeding plans.

Techniques have been developed to introduce specific genes from one species into the germplasm of another, including livestock. This paper reviews reports on evaluation, selection, and breeding procedures for introduction and multiplication of transgenes in breeding populations of livestock. Before transgenes are introduced and multiplied in commercial breeding populations, it is necessary to test transgenics extensively for both favorable and unfavorable transgene effects. Parent stock used to produce transgenic founder animals should be selected to excel in polygenic breeding value for economically important traits, especially if founder animals or their sons are to be used directly by AI in commercial populations. However, polygenic breeding value of founder transgenic animals and inbreeding depression are of negligible importance if a transgene is introgressed into a selection nucleus population from three or four generations of backcrossing. Transgenic development should be economically viable for traits with major effects on net merit, especially in the dairy industry, where transgenic sires can be used extensively by AI. A minimum effect of about 10% of the mean (or one phenotypic standard deviation) is a reasonable approximation of the minimum transgene effect that would be necessary to justify introgression into a nucleus swine population. A transgene effect of 10 to 20% of the mean would be required for most economic traits in beef cattle.

Animals↗

Scaling to account for heterogeneous variances in a Bayesian analysis of broiler quantitative trait loci.

A Bayesian method for QTL analysis that is capable of accounting for heterogeneity of variance between sexes, is introduced. The Bayesian method uses a parsimonious model that includes scaling parameters for polygenic and QTL allelic effects per sex. Furthermore, the method employs a reduced animal model to increase computational efficiency. Markov Chain Monte Carlo techniques were applied to obtain estimates of genetic parameters. In comparison with previous regression analyses, the Bayesian method 1) estimates dispersion parameters and polygenic effects, 2) uses individual observations instead of offspring averages, and 3) estimates fixed effect levels and covariates and heterogeneity of variance between sexes simultaneously with other parameters, taking uncertainties fully into account. Broiler data collected in a feed efficiency and a carcass experiment were used to illustrate QTL analysis based on the Bayesian method. The experiments were conducted in a population consisting of 10 full-sib families of a cross between two broiler lines. Microsatellite genotypes were determined on generation 1 and 2 animals and phenotypes were collected on third-generation offspring from mating members from different families. Chromosomal regions that seemed to contain a QTL in previous regression analyses and showed heterogeneity of variance were chosen. Traits analyzed in the feed efficiency experiment were BW at 48 d and growth, feed intake, and feed intake corrected for BW between 23 and 48 d. In the carcass experiment, carcass percentage was analyzed. The Bayesian method was successful in finding QTL in all regions previously detected.

Animals↗