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PubMed1975

The mating system and microevolution.

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.

Adaptation, Biological↗
PubMed2003

[Negative selection and computer models of the joint evolution of the patterns of polygenes, transposable elements, and origin identity labels].

Computer simulation of the population dynamics of the genomic patterns of polygenes, transposable elements (TEs), and origin identity labels (OILs) in the course of negative selection for an additive quantitative trait has been performed. It was demonstrated that active polygene alleles disappear very rapidly, whereas the patterns of TEs and OILs continue their evolution determined by strict selective inbreeding and gene drift. Dendrograms of the patterns of polygenes, TEs, and OILs were constructed for all generations. It was demonstrated that the final consensus pattern of OILs consists of the fragments of the original patterns, which contain neither active polygene alleles nor modifier or marker TEs. Neutral TE copies were present in the final pattern, as should be expected in the case of gene drift. Inbreeding coefficient increased steadily but by generation 100 reached values higher than 0.9. All other parameters and initial conditions being the same, the responses to negative and positive selections were asymmetric.

Animals↗
PubMed2003

[Stabilizing selection and computer models of the joint evolution of patterns of polygenes, transposable elements, and origin identity labels].

A computer model of the populations dynamics of the patterns of polygenes, transposable elements (TEs), and origin identity labels (OILs) in the course of stabilizing selection for an additive quantitative trait (with the target value being 0.4 of the maximum) was analyzed. It was demonstrated that the final plateaus of the trait value and the frequencies of the active values of polygenes are reached rapidly, namely, within five to seven generations (the effective selection period). The inbreeding coefficient during this period also grows rapidly and then gradually increases eventually reaching approximately 0.7. The inbreeding coefficient reaches plateau (at approximately 1.0) only in generations 300-350, which suggests the effect of gene drift. Dendrograms of the patterns of polygenes, TEs, and OILs were constructed for all generations. By generation 100 of selection, the final patterns of TEs and OILs were not formed completely. Fixations and losses, especially those of the OIL pattern, were delayed. In general, however, the population heterogeneity with respect to the patterns studied does not stabilize. This heterogeneity decreases the case of stabilizing selection, although more slowly than in the cases of positive and negative selections.

Animals↗
PubMed1975

[A neurogenetic study in an inbred population].

A Tatar family from a semi-isolated village in the Gorky Region is described in which a neurological and ophthalmological syndrome was inherited. In homozygotes this syndrome comprised the degeneration of subcortical cerebral ganglia (hyperkinesis), nystagmus, oligophrenia and a peculiar variant of tapetoretinal degeneration. Heterozygotes exhibited ophthalmological abnormalities, such as the similar defects of eye bottom and nystagmus. The two homozygotes observed were sibs derived from a marriage between first cousins. Five more families with other rare hereditary anomalies (both dominant and recessive) were discovered in this village. The total inbreeding coefficient in the village was found to be 0.0075. The high degree of inbreeding, subisolation and high fertility are regarded as factors favorable for the distribution of rare deleterious mutations due to the founder-effect.

Adult↗
PubMed2003

[Population genetic analysis of the heritability of gutteral pouch tympany in Arabian purebred foals].

The objective of the present study was to analyse the importance of the influences of the sex, inbreeding coefficient and the additive genetic contribution to the occurrence of guttural pouch tympany in Arabian foals. Horses affected by guttural pouch tympany were ascertained in the Clinic for Horses, School of Veterinary Medicine Hannover. The data comprised 27 Arabian purebred foals with guttural pouch tympany. Of these 27 animals 22 were patients of the Clinic for Horses between 1994 and 2001 and 5 Arabian foals were sampled on the studs. Information on the pedigrees of these patients allowed us to sort in the affected foals into four families with a total of 276 animals. Female foals were more often affected by guttural pouch tympany. The difference was 11.9% in favour of female foals. The size of the inbreeding coefficient was not important for the occurrence of guttural pouch tympany. The heritability estimate for the frequency of guttural pouch tympany using a threshold model was 0.49 +/- 0.28. This is the first report that could show a genetic component responsible for guttural pouch tympany in foals.

Animals↗
PubMed1977

[Medico-genetic study of the population of the Samarkand region. II. Population-genetic description of 4 kishlaks of the Urgut district].

This report is a second one in a series of works devoted to the medico-genetical screening of Uzbekistan populations. The paper comprises the results of the analysis of the populational structure of one of the village councils (soviets) of the Urgut District of the Samarkand Region. The main parameters of the population studied were as follows: total number 1529 persons, the average number of inhabitants of one village--328. The proportion of the inhabitants studied--56%, the average number of persons per family--5.22; the average period between subsequent generations--30-35 years, the gametic index--0.8, the inbreeding coefficient inferred from pedigrees--0.018899--0.00781, Fst = 0.03577, the average genetic distanse according to Edwards--0.0231-0.0671. The distribution of Mendelian markers (ABO, Rh, Hp and Ptc) was studied. The observed ratio between a high degree of inbreeding and a relatively low extent of isolation of populations permits to explain satisfactorily the distribution and frequencies of hereditary pathology in the Urgut District of the Samarkand Region pointed out in the previous report.

Adolescent↗
PubMed1977

[Medico-genetic study of the population of Uzbekistan. III. Phenotypical assortativity as a factor in population structure (using palmoplantar hyperkeratosis and vitiligo as examples)].

The article comprises the examples of homophenogamic marriages between persons with a rare hereditary dominant character, hand-palm and foot-sole hyperkeratosis, leading to the increase of inbreeding intensity in the population. On the contrary, homophenogamic marriages between persons with vitiligo, a considerably more widespread character, lead to the decrease of the degree of inbreeding in a population, since they take place between partners coming from different districts of the region.

Female↗
PubMed2005

Self-fertilization and the escape from pollen limitation in variable pollination environments.

Seed production in many plants is pollen limited, likely because of unpredictable variation in the pollinator environment. One way for plants to escape the consequences of pollinator variability is to evolve mating systems, such as autonomous selfing, that assure reproduction without relying on pollinators. We explore this hypothesis through the construction and analysis of heuristic models of plant population dynamics in seed- or site-limited populations. Our analysis suggests several important points: the familiar rule that inbreeding depression greater than 0.5 maintains outcrossing significantly underestimates the threshold required under pollen limited conditions with prior selfing; variability in the pollination environment erodes the ability of inbreeding depression to maintain outcrossing; and variable pollination environments can result in stable intermediate rates of prior selfing. The results reflect the importance of geometric mean fitness (which in a variable environment is less than the arithmetic mean) in the face of temporal variation.

Genetics, Population↗
PubMed1992

Actinomycetales infections in slender-horned gazelles: six cases (1987-1989).

Disseminated Actinomycetales infections were diagnosed in 6 slender-horned gazelles at a zoologic park over a 17-month period. Nocardia and Mycobacterium spp were isolated. Possible predisposing causes leading to infection were investigated. Environmental contamination where the gazelles were housed was not high, and other breeds of gazelles at the park did not become infected, indicating that environmental exposure was not the sole factor involved. Information gathered from questionnaires sent to other zoologic parks and personnel communications indicated that this was not an isolated incident. Investigation into the genetic lineage of the gazelles revealed substantial inbreeding in prior generations. These findings suggested inbreeding may have been an important predisposing factor leading to infection. Careful scrutiny to ensure maximal heterozygosity of future breedings is warranted.

Actinomycetales Infections↗
PubMedDate not supplied

[Genetic-statistical analysis of environmental and genetic influences on the outcome of the juvenile and breeding performance tests for behaviour traits in Hovawart dogs].

The objective of the present study was to evaluate the importance of genetic and environmental sources of variation for results of behaviour tests recorded at juvenile and breeding performance tests in the Hovawart dog. For these analyses behaviour test results of 1882 (juvenile evaluation), respectively 929 dogs (breeding performance test) born in 1995 to 2000 had been used. Variance component estimation was performed for the traits appearance, play instinct, hunting affinity, group of people, shoot, acoustical and optical influences and temperament using multivariate linear animal models and Residual Maximum Likelihood (REML). The models included test-year-season, sex, litter size, age and inbreeding coefficient of the animal as fixed effects. Additive genetic effects of the animal, permanent environmental effect of the litter and the effect of the kennel were considered as random factors. The sex of the dog was significant for appearance, play instinct, hunting affinity, acoustical and optical influences of juvenile evaluation and for the traits temperament, play instinct, hunting affinity, acoustical and one of the optical influences of breeding performance test. The age of the dog at test significantly influenced the traits play instinct, hunting affinity and acoustical influences of juvenile evaluation and optical influences and hunting affinity of breeding performance test. All traits with exception of hunting affinity and group of people were significantly affected by the test-year-season. The inbreeding coefficient was significant for appearance of juvenile evaluation and play affinity of breeding performance test. The effect litter size did not influence any of the traits significantly. The estimated heritabilities for the behaviour traits of juvenile and breeding performance test ranged from h2 = 0.01 to h2 = 0.13, respectively h2 = 0.01 to h2 = 0.14, with standard errors of up to 0.03. The additive genetic correlations between most of the traits were moderately to highly positive (r(g) = 0.20 to r(g) = 1.0, respectively r(g) = 0.29 to r(g) = 1.0). Negative additive genetic correlations were only found for a few traits of juvenile (r(g) = -0.02 to r(g) = -0.58) and breeding performance test (r(g) = -0.28 to r(g) = -0.83). Progress in breeding for the behaviour traits investigated here may only be meaningful when information from all relatives is used in an animal model instead of selection based on the phenotype of the single animal.

Age Factors↗
PubMed2006

[Genetic influences on the outcome of the progeny tests for behaviour traits in Hovawart dogs].

The objective of the present study was to evaluate the importance of genetic and environmental sources of variation for results of behaviour tests in young dogs being used for progeny evaluations in the Hovawart dog. In total, 4,113 dogs born in 1995 to 2000 have been available for these analyses. Traits used were appearance, hunting affinity, group of people, acoustical and optical influences and temperament. Variance components were estimated using multivariat linear animal models and Restricted Maximum Likelihood (REML). The models included test-year-season, sex, litter size, age and inbreeding coefficient of the animal as fixed effects. Additive genetic effects of the animal, permanent environmental effect of the litter and the effect of the kennel were considered as random factors. The sex of the dog was significant for all traits. The age of the dog at the test significantly influenced the traits temperament and appearance. Test-year-season was significant for all traits except for appearance, whereas the inbreeding coefficient of the animal was significant for acoustical influences and temperament. Litter size did not influence any of the traits significantly. The estimated heritabilities of the behaviour traits analysed here ranged from h2 = 0.03 to h2 = 0.11 with standard errors of up to 0.03. The additive genetic correlations between most of the traits were moderately to highly positive (rg = 0.16 to rg = 0.91). The traits hunting affinity and appearance showed an additive genetic correlation close to zero (rg = 0.03). Negative additive genetic correlations were found between temperament and appearance as well as acoustical and optical influences (rg = -0.14 to rg = -0.4).

Age Factors↗
PubMed1989

Estimation of genetic parameters among reproductive and growth traits in yearling heifers.

Growth and reproductive data were obtained on 779 beef heifers at the San Juan Basin Research Center, Hesperus, Co. Genetic parameters were estimated for age of puberty (AOP), age of first calving (AOC), julian day of first calving (DOC), julian day of second calving (DOSC), birth weight, weaning weight, yearling weight, and average daily gain from weaning to yearling and to cycling weights. The least squares model included birth year, age of dam and breed as fixed effects, sire/breed as a random variable, and day of birth and percent inbreeding as covariates. Day of birth was not included in the analyses of AOC, DOC or DOSC. Paternal half-sib estimates of heritability were: AOP, .10 +/- .17; AOC, .01 +/- .12; DOC, .09 +/- .13 and DOSC, .36 +/- .18. Genetic and phenotypic correlations were generally favorable, but genetic correlations were variable with large standard errors. Inbreeding had a detrimental effect on reproductive traits, and a seasonal effect was present for AOP.

Age Factors↗
PubMedDate not supplied

[Anomalous origin of the left coronary artery at the pulmonary trunk and its relationship with other primary coronary anomalies: experimental study].

The origin and course of the coronary arteries were studied in 1,436 Syrian hamsters belonging to 10 breeding colonies subjected to high endogamous pressure by mating either animals of the same litter or first cousins. The study was carried out using a corrosion casting technique. A left coronary artery originating from the pulmonary trunk was found in 48 specimens of the series. In all cases anastomoses had developed between the right and left coronary systems. Moreover, five types of minor primary anomalies of the coronary arteries occurred in 144 hamsters. These findings agree with the morphogenetic hypothesis that each of the aortic and pulmonary sinuses has the potential to develop coronary arteries. Familial recurrence risks for coronary arterial anomalies were estimated taking into account the sex and the inbreeding coefficient of the probands carrying a left coronary artery from the pulmonary trunk. The recurrence risks increase as the inbreeding level increases, this suggesting that the whole primary coronary anomalies are a phenotypic set subordinated to a complex mode of inheritance. Therefore, an echocardiographic study of the first degree relatives of patients with coronary arterial anomalies is advisable to diagnose clinically silent coronary malformations.

Animals↗
PubMed1977

The influence of the mating system on the maintenance of genetic variability in polygenic characters.

The traditional models of the effect of assortative mating and inbreeding on the genetic variance of polygenic characters (FISHER 1918; WRIGHT 1921) presume that there is no natural selection or mutation. In a large population, the genetic variance determined by additive genes may then increase by up to a factor of two with local inbreeding, and even more with assortative mating. The classical models are still used to interpret data from natural populations. But contrary to their assumptions, most metrical characters in natural populations are usually thought to be under a type of selection which depletes polygenic variation. Mutation is then necessary to maintain genetic variation. The present models show that with the additional features of mutation and selection, in a large population, the mating system has no influence on the amount of genetic variability maintained by additive genes.

Animals↗
PubMedDate not supplied

Genetic considerations in human cancer incidence.

Analysis by the methods of genetic demography can offer plausible explanations for the unusual distribution of cancer in an area of high incidence. The important demographic characteristics include inbreeding, founder effect, and racial admixture. Inbreeding would elevate cancer incidence if autosomal recessive genes played a role in cancer etiology. Founder effect would limit this phenomenon to those recessive genes observed in the founding group and result in a cancer spectrum different from that of the surrounding populations. The preference of a racially admixed group for classification as white could result in an excess of cancer patients being classified as white. The population groups in southern Louisiana typify the kind of "human genetics laboratory" that inbred groups offer to investigators of the genetic aspects of cancer.

Adult↗
PubMed1977

Breeding of a rabbit strain of hyperlipidemia and characteristic of this strain (author's transl).

We attempted the breeding experiment in order to establish an inbred strain of disease model animal derived from a spontaneously hyperlipidemic rabbit (HLR). The clinical, pathological features and breeding results of HLR strain were as follows; 1) A prominent clinical feature of this strain was conspicuous elevation of serous lipid ingredients including cholesterol (S-ch), beta-lipoprotein (beta-LP). The S-ch level was 400 +/- 70 mg/dl, the beta-LP level 9.1 +/- 1.5 unit and the total lipid 1146 +/- 270 mg/dl in the HLR strain. These values were approximately 9, 10 and 4 times higher than those of normal rabbits respectively. 2) After sacrifice, aterosclerotic lesions were evident extensively in the aorta and renal arteries. Nodular of plane xanthomas were conspicuous over the articuli digitorum of manus and pedis. 3) HLR strain indicated a striking resemblance of the condition to type III hyperlipidemia in the Frederickson's classification of hyperlipidemia in man. 4) Inbreeding was carried out in two lines, viz. sister-brother mating, parent-offspring mating and back crossing. As the result, the second filial generation showed an incidence of HLR of 15.0%, the third generation 50.0%, and the fourth generation 56.1% respectively. In the fourth generation, the coefficients of inbreeding and relationship were 50% and 72.3% respectively.

Animals↗
PubMed1996

Genetic studies in Medzev, an isolate in south-eastern Slovakia. 1. History, demography, marriage patterns.

In Medzev, a village located in South-Eastern Slovakia, the secular variation of two indices of genetic isolation has been studied. It could be seen that this village was highly isolated till the beginning of the 20th century. Both indices show a tendency to increase in the first five decades of this century. For the entire period from 1766-1950 the coefficient of inbreeding estimated by the method of isonymy was found to be F = 0.0074 with different ratios of random (Fr) and non-random (Fn) components in particular periods. The coefficient of inbreeding estimated from the ecclesiastical dispensations for marriages comes to F = 0.0019. The genetic significance of the changes in the population structure of this village will be analyzed in further studies.

Ethnicity↗
PubMed1994

Consanguineous matings in an Israeli-Arab community.

OBJECTIVE: To determine the frequency of consanguineous marriages and the inbreeding coefficient in Israeli Arabs. DESIGN: Cohort survey. SETTING: General community in 70 settlements in Israel. PARTICIPANTS: Nine thousand three hundred Israeli-Arab students in the second grade were sent questionnaires to be filled out by their fathers, with 8521 completed questionnaires returned. INTERVENTIONS: None. MEASUREMENTS/MAIN RESULTS: Of the 8521 completed questionnaires, 1156 (14%) were from urban areas, 2267 (27%) were from suburban areas, and 5098 (60%) were from rural areas. The prevalence of consanguineous matings in the studied group was 44.3%, with a mean inbreeding coefficient of .0192. This prevalence is high and was highest in the rural areas. Marriages between first cousins occurred more often than marriages between other relatives in all locations. CONCLUSION: The frequency of consanguineous marriages is quite high among Israeli Arabs, approaching 50%.

Consanguinity↗