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PubMed1996

A study of inbreeding and kinship in intracranial aneurysms in the Saguenay Lac-Saint-Jean region (Quebec, Canada).

The genealogies of 533 individuals with an intracranial aneurysm (IA) born in the Saguenay-Lac-Saint-Jean region, a geographically isolated area located in northeastern Quebec, were reconstructed using a population-based register. A control group consisting of three individuals of the same sex and born on the same day and in the same municipality than the IA patients was created; the genealogies of the 1599 controls were also reconstructed. The coefficients of inbreeding and kinship were calculated. Familial aggregation, i.e. the presence of IA in two or more first- to third-degree relatives, was also sought. The mean inbreeding coefficient was lower in the IA group than in the control group (7.92 x 10(-4) versus 10.04 x 10(-4)). The mean kinship coefficient was higher in the IA group than in the control group (2.17 x 10(-4) versus 1.55 x 10(-4)). Forty-eight IA patients (9.0%) were first-degree relatives compared to only 1.9% of the control individuals. The proportion of individuals showing familial aggregation was higher in the IA group than in the control group (29.8% and 18.6% respectively). These results strongly suggest that some IA are genetically determined in this population.

Consanguinity↗
PubMed2006

Estimating human inbreeding coefficients: comparison of genealogical and marker heterozygosity approaches.

We have used genealogies and genomic polymorphisms to estimate individual inbreeding coefficients (F) in 50 subjects with an expected range (based on recent genealogies) of F from 0.0 to 0.0625. The estimates were based on two approaches, using genotypes respectively from 410 microsatellite markers (410-STR panel) and from 10,000 SNPs (10K-SNP panel). The latter was performed in a sub-sample of 15 individuals. We concluded that for both marker panels measures of inbreeding based on the excess of homozygosity over Hardy-Weinberg expectation were not closely correlated with 4-5 generation genealogical F-values. For the 10K-SNP panel we found two alternative measures which correlated more closely with F, based respectively on standard errors and on paired homozygosity of nearby SNPs over distances of 2-4 cM. We propose an empirical method for estimating standard errors and hence individual F-values, based on the variation between individual autosomes. This method could provide useful estimates of average F-values for groups of individuals in population-based studies of the effects of inbreeding/homozygosity on quantitative traits.

Consanguinity↗
PubMed2006

Recombinant inbreeding in mice reveals thresholds in embryonic corpus callosum development.

The inbred strains BALB/cWah1 and 129P1/ReJ both show incomplete penetrance for absent corpus callosum (CC); about 14% of adult mice have no CC at all. Their F(1) hybrid offspring are normal, which proves that the strains differ at two or more loci pertinent to absent CC. Twenty-three recombinant inbred lines were bred from the F(2) cross of BALB/c and 129, and several of these expressed a novel and severe phenotype after only three or four generations of inbreeding - total absence of the CC and severe reduction of the hippocampal commissure (HC) in every adult animal. As inbreeding progressed, intermediate sizes of the CC and the HC remained quite rare. This striking phenotypic distribution in adults arose from developmental thresholds in the embryo. CC axons normally cross to the opposite hemisphere via a tissue bridge in the septal region at midline, where the HC forms before CC axons arrive. The primary defect in callosal agenesis in the BALB/c and 129 strains is severe retardation of fusion of the hemispheres in the septal region, and failure to form a CC is secondary to this defect. The putative CC axons arrive at midline at the correct time and place in all groups, but in certain genotypes, the bridge is not yet present. The relative timing of axon growth and delay of the septal bridge create a narrow critical period for forming a normal brain.

Agenesis of Corpus Callosum↗
PubMed1993

Early child health in Lahore, Pakistan: II. Inbreeding.

The prevalence of consanguineous marriages was studied in 940 families belonging to four different socio-economic groups in and around Lahore, Pakistan. The births occurring in these families from September 1984 to March 1987 were also investigated for birth defects. The overall prevalence of consanguineous marriages was 46%. The first cousin marriages were most common (67%), followed by the marriages between second cousins, 19%. The prevalence of consanguineous marriages was clearly associated with the socio-economic status of the study groups; 50% of the marriages was related in the periurban slum, 49% in the village, 44% in the urban slum and 31% in the upper middle class. The birth defects were also more prevalent in the poorer areas, being highest in the periurban slum (17.7%) followed by the urban slum (15.6%) and then the village (14.8%) and lowest in the upper middle class (12.3%). Although, the frequency of both consanguinity and birth defects were related with the socio-economic levels of the study groups, there was no association between inbreeding and birth defects. Perhaps, deleterious recessive genes for birth defects have been "bred out", because of continuous inbreeding over generations in this population. There was a significant predilection of major birth defects in boys without clear sex linkage. The conclusion is that the rate of consanguineous marriages was high, especially in the poorer areas, but the relationship between consanguineous marriages and birth defects was little or none. However, other child health indicators may be affected by consanguineous marriages.

Adult↗
PubMed1990

Inbreeding effects on reproductive outcome in a Sudanese population.

926 women attending the Obstetrics and Gynaecology Department of the Faculty of Medicine, Khartoum, were investigated to study the inbreeding effects on reproductive profiles and morbidity of the offspring. 49.5% of the women had married their first cousins and 13.8% had married more distant relatives. Altogether, 4,471 pregnancy outcomes were analysed including abortions, still births, neonatal and childhood deaths, physical deformity, mental retardation and other congenital abnormalities. No significant difference in the reproductive loss or net fertility was observed between the inbred and outbred groups. Only the proportions of childhood deaths were found to be significantly higher in the inbred marriages (p less than 0.005). The morbidity was also not affected by the practice of inbreeding.

Congenital Abnormalities↗
PubMed1993

A five-year prospective study of the health of children in different ethnic groups, with particular reference to the effect of inbreeding.

A 5-year prospective study of 4,934 children of different ethnic groups has demonstrated a 3-fold increase of postneonatal mortality and childhood morbidity in the offspring of consanguineous Pakistani parents. Most of these families contained more than one consanguineous union, resulting in a mean inbreeding coefficient for their children of 0.0686. It is estimated that 60% of the mortality and severe morbidity of this group of children could be eliminated if inbreeding ceased. However consanguinity is much favoured in this minority group, and health education will have to be carefully and sensitively handled.

Bangladesh↗
PubMed2004

Effect of inbreeding on Wechsler intelligence test scores among North Indian children.

The effects of inbreeding in humans on the intelligence has been investigated in the present study of offspring of second cousin matings (F=0.0156, n=138 male, 132 female), first cousins once removed (F=0.03125, n=148 male, 138 female), first cousins (F=0.0625, n=161 male, 151 female), and unrelated (F=0, n=194 male, 182 female) among North Indian Muslims. The Weschler Intelligence Scale for Children (WISC-R)-74 was given to the children in the both groups. An overall significant (p<0.001) reduction of means has been observed in inbred series. The results of this study confirm the appreciable inbreeding depression especially among the offspring of first cousins.

Child↗
PubMedDate not supplied

Mating schemes for optimum contribution selection with constrained rates of inbreeding.

The effect of non-random mating on genetic response was compared for populations with discrete generations. Mating followed a selection step where the average coancestry of selected animals was constrained, while genetic response was maximised. Minimum coancestry (MC), Minimum coancestry with a maximum of one offspring per mating pair (MC1) and Minimum variance of the relationships of offspring (MVRO) mating schemes resulted in a delay in inbreeding of about two generations compared with Random, Random factorial and Compensatory mating. In these breeding schemes where selection constrains the rate of inbreeding, DeltaF, the improved family structure due to non-random mating increased genetic response. For schemes with DeltaF constrained to 1.0% and 100 selection candidates, genetic response was 22% higher for the MC1 and MVRO schemes compared with Random mating schemes. For schemes with a less stringent constraint on DeltaF or more selection candidates, the superiority of the MC1 and MVRO schemes was smaller (5-6% ). In general, MC1 seemed to be the preferred mating method, since it almost always yielded the highest genetic response. MC1 mainly achieved these high genetic responses by avoiding extreme relationships among the offspring, i.e. fullsib offspring are avoided, and by making the contributions of ancestors to offspring more equal by mating least related animals.

Journal Article↗
PubMed2005

The evolution of cytoplasmic incompatibility types: integrating segregation, inbreeding and outbreeding.

Cytoplasmic incompatibility (CI) is a reproductive incompatibility induced by maternally transmitted bacteria of the genera Wolbachia and Cardinium. In the simplest form of CI, offspring from infected males and uninfected females suffer from increased mortality. However, it has been noted that crosses between males and females carrying different strains of infection are often also incompatible. The evolutionary processes leading to the emergence of new CI-compatibility types are still not resolved. Here, we develop a model that extends previous theoretical approaches by including segregation of bacterial strains during transmission as well as a continuum of breeding systems ranging from inbreeding (complete sib mating) to outbreeding (complete sib-mating avoidance). Our results demonstrate that (1) with segregation of strains, evolution is unlikely to lead to new CI types that co-occur as a double infection with the preexisting one, (2) inbreeding substantially hampers the evolution of new CI types, and (3) outbreeding facilitates the evolution of new CI types. Our model also provides a hypothesis on the evolutionary origin of CI.

Bacteria↗
PubMedDate not supplied

[Inbreeding coefficient in carriers of Schistosoma mansoni].

The coefficient of inbreeding (for Wright) was studied in Catolândia, in the state of Bahia, Brazil, an area considered hyperendemic for manson schistosomiasis in a population of 1,130 inhabitants. The coefficient of inbreeding was estimated for 1,123 individuals it was classified as f greater than 0 in 13.2% (n = 148). In the hepatosplenic group the frequency of f greater than 0 was 26.8%, and in the hepatointestinal group the frequency was 12.5%. The frequency of the hepatosplenic diagnosis in whites who were f = 0 did not differ from that which was observed in the negroid group. These verifications were confirmed by the Woolf's test; the relative risk of the whites, f greater than 0 in acquiring hepatosplenic schistosomiasis was 14.1. These observations reinforce the influence of the genetic component in the development of the hepatosplenic form of the mansons schistosomiasis.

Brazil↗
PubMed1999

The effect of inbreeding on early childhood mortality: twelve generations of an Amish settlement.

An unresolved issue in research on child survival is the extent to which familial mortality risk in infancy is due to biological influences net of sociodemographic and economic factors. We examine the effect of consanguinity on early childhood mortality in an Old Order Amish settlement by using the inbreeding coefficient, an explicit measure of the degree of relatedness in one's ancestry. Inbreeding has a net positive effect on neonatal and postneonatal deaths. We find social, demographic, and population-based sociocultural explanations for this effect among the Amish population which is known to experience certain genetically transmitted defects associated with mortality.

Adult↗
PubMed1999

[Genetic demographic characteristics of the rural population of the Tuva Republic: marriage structure and inbreeding].

Marriage structure was studied in three rural populations of the Tuva Republic: the Shinaan population and the populations of Todzhinskii and Bai-Taiginskii raions (districts). The Shinaan and Bai-Taiginskii populations had high levels of endogamy (0.6704 and 0.6050, respectively). In the Todzhinskii population, which was characterized by a mixed ethnic composition, endogamy was 0.3779 for the total population and 0.4626 for Tuvinians; interethnic marriages in this population were rare. The values of marriage assortativeness with respect to birthplace were 19.38, 40.75, 75.87, and 41.87% in the Shinaan, Bai-Taiginskii, all the Todzhinskii populations, and Tuvinian monoethnic marriages in the Todzhinskii raion, respectively. High marriage assortativeness with respect to ethnicity was found. Its values (A') were 91.85 and 93.49% in Tuvinians and Russians, respectively. Tuvinian populations were characterized by high inbreeding. The total (F(it)), random (Fst), and nonrandom inbreeding (Fis) estimated by isonymy were 0.004237, 0.002298, and 0.001944 in the Shinaan population, 0.007292, 0.009448, and -0.002177 in the Bai-Taiginskii population, and 0.003846, 0.004152, and -0.000307 in the Todzhinskii population, respectively (in the latter populations, the F(it), Fst, and Fis values for Tuvinian marriages alone were 0.005000, 0.007222, and -0.002238, respectively). The results obtained indicate that individual territorial groups of Tuvinians retain a high degree of genetic isolation from one another.

Adult↗
PubMed2000

Prediction of rates of inbreeding in populations selected on best linear unbiased prediction of breeding value

Predictions for the rate of inbreeding (DeltaF) in populations with discrete generations undergoing selection on best linear unbiased prediction (BLUP) of breeding value were developed. Predictions were based on the concept of long-term genetic contributions using a recently established relationship between expected contributions and rates of inbreeding and a known procedure for predicting expected contributions. Expected contributions of individuals were predicted using a linear model, u(i)(()(x)()) = alpha + betas(i), where s(i) denotes the selective advantage as a deviation from the contemporaries, which was the sum of the breeding values of the individual and the breeding values of its mates. The accuracy of predictions was evaluated for a wide range of population and genetic parameters. Accurate predictions were obtained for populations of 5-20 sires. For 20-80 sires, systematic underprediction of on average 11% was found, which was shown to be related to the goodness of fit of the linear model. Using simulation, it was shown that a quadratic model would give accurate predictions for those schemes. Furthermore, it was shown that, contrary to random selection, DeltaF less than halved when the number of parents was doubled and that in specific cases DeltaF may increase with the number of dams.

Journal Article↗
PubMed2001

Cross-fertility in two tropical tree species: evidence of inbreeding depression within populations and genetic divergence among populations.

Knowing the spatial patterns of cross-fertility in natural plant populations yields key insight into biparental inbreeding depression, isolation by distance, and, ultimately, speciation. Three adults each of two tropical tree species (Syzygium rubicundum and Shorea cordifolia) were each crossed with five conspecific pollen donors ranging from self to trees occurring in separate forest reserves (12 and 35 km distance for S. rubicundum and Sh. cordifolia, respectively). Cross-fertility was estimated as fruit set, seed germination, and seedling survivorship and height at 1 yr. Means of most cross-fertility measures increased steadily with outcrossing distance, peaking at 1-2 km for S. rubicundum and 1-10 km for Sh. cordifolia, and then declining at the between-forest crosses. However, seed germination and seedling height for Sh. cordifolia suggested hybrid vigor in between-forest crosses. The mean fitness cost of nearest-neighbor mating relative to crossing with more distant neighbors was 45% for S. rubicundum and 0% for Sh. cordifolia. The mean fitness cost of between-forest crosses was 52% and 70% for the two species. Crossing effects on fitness diminished between the stages of fruit set and 1-yr-old seedlings. Results indicate a strong potential for inbreeding depression within forest tree populations and partial reproductive isolation among forests in Sri Lanka's wet zone.

Journal Article↗
PubMed2006

Effects of inbreeding, endogamy, genetic admixture, and outbreeding on human health: a (1001 Dalmatians) study.

AIM: (1001 Dalmatians) research program collects biomedical information from multiple small isolated populations ((metapopulation)) on Adriatic islands, Croatia, and investigates health effects of human population isolation, inbreeding, admixture, and outbreeding. METHODS: We collected random samples of 100 individuals from 9 island settlements and an additional sample of 101 immigrants to the islands, pooled from all study populations. According to their personal genetic histories, the examinees were categorized as inbred, autochthonous, admixed, and outbred. A total of 76 inbred individuals from a total sample of 1001 examinees were matched to 76 autochthonous, 76 admixed, and 76 outbred controls by gender, age (+/-5 years), village of residence, education, and socio-economic status. We investigated the effects of presumed individual genome-wide heterozygosity predicted from personal genetic histories on the following 10 traits: systolic and diastolic blood pressure, body mass index, high and low density lipoproteins and total cholesterol, triglycerides, uric acid, creatinine, and blood glucose. RESULTS: Personal genetic history significantly affected systolic blood pressure (Spearman rho=0.157, P=0.006), while the effect on cholesterol (rho=0.105, P=0.069), and high density lipoprotein cholesterol (rho=0.104, P=0.071) was suggestive. Admixed individuals and immigrants consistently showed values associated with lower health risk. When inbred and autochthonous samples were merged and compared with the admixed and outbred samples to increase the power of the study, the effects on the three traits above and also on body mass index and diastolic blood pressure became statistically significant. The medians for all 10 medically relevant traits in inbred and autochthonous group, with lower values of presumed individual genome-wide heterozygosity, were less favorable in terms of health. CONCLUSION: The combined effects of founder effect, genetic drift, and inbreeding can increase the frequency of detrimental rare variants in human metapopulations, leading to overall worsening of population health, whereas admixture and outbreeding appear to have the opposite effect.

Adult↗
PubMed1988

[Genetic demographic approach in anthropological research. IV. The information value of genealogical tables and the level of inbreeding in Khakass populations].

The average volume of genealogical information in two Khakass ethnographic groups--Kizil and Sagai populations was 0.451 and 0.331 taking into account 7 and 10 generations under study correspondingly. The inbreeding coefficients calculated with the help of genealogical method are 0.0012 and 0.0025 and using the group of potentially or conditionally consanguineous marriages--0.0051 and 0.0108. The common inbreeding coefficient (FIT) and relative impact into it of the random (FST) and nonrandom (FIS) components received by means of the isonymy method in Kizil ethnographic group were 0.0121, 0.026 and -0.0143, while in the Sagai group the figures were 0.020, 0.042 and -0.023. The collection and analysis of the genealogical information presented non-graphically gives wide opportunities in description of the population structures as well in a number of allied branches of science where the genealogical (graphic) method is used.

Anthropology, Physical↗
PubMed1985

Inbreeding and matrimonial structure in a Pyrenean community (Ansó, Huesca, Spain), 1712-1982.

Using data from parish records from 1712 to 1982 in a Spanish Pyrenean village, Ansó, the effects of the raw nuptiality, the types of consanguineous marriages and the rate and evolution of inbreeding on the mating structure have been studied. This structure has been modified in the course of time mostly through the secular variations in the frequency of consanguineous marriages. Recent inbreeding decrease in Ansó is related to the population diminution and cultural changes associated with isolate breakdown.

Consanguinity↗
PubMed1985

Estimation of inbreeding by isonymy in Iberoamerican populations: an extension of the method of Crow and Mange.

The method of isonymy for the estimation of inbreeding levels was extended to use the potentialities offered by the Iberoamerican surname system, in which a child inherits his surnames both from the father and the mother. Four possible types of isonymy were recognized between the family names of a husband-wife pair. It was found that, limited to simple consanguinity, the ratio between isonymy and the inbreeding coefficient of consanguineous individuals, starting from first cousins, is constant and equal to 16. Consanguinity levels were studied in four Venezuelan groups, Isla de Toas, Los Teques, Quibor, and Colonia Tovar, using genealogies, classical isonymy, and the extended method. It was found that, for Iberoamerican populations, the extended method is more precise than the classical method.

Consanguinity↗