scholarly journals On The Influence of Genetic Factors on the Formation of Homosexuality by Data of Twin Studies

2019 ◽  
Keyword(s):  
Sexual Orientation ◽  
Genetic Factors ◽  
Dominant Role ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Correct Selection ◽  
Genetic Determination ◽  
Dizygotic Twins

Results of twin studies are presented; these demonstrate that in a number of cases genetic effects can play a role of mild predisposing factors for the development of homosexuality, but the main part in its formation is accounted for by psychological and social factors. The opinion that genetic factors play the only and dominant role in the genesis of homosexuality does not hold water due to the fact that if it were so then their concordance for homosexuality in monozygotic twins would be 100 %, but it is not observed in reality. The studies conducted with the correct selection of examinees revealed 20 % of the concordance for homosexuality in male monozygotic twins and 24 % in female ones (Bailey, J.M., et al. Genetic and environmental influences on sexual orientation and its correlates in an Australian twin sample. J. Pers. Soc. Psychol. 78(3), 524‑536). The use of Holzinger’s formula for analyzing the obtained numerical findings demonstrated that in the above case the proportion between heritable and environmental factors for male persons was 0.2 (20 %) versus 0.8 (80 %), for female persons it being 0.15 (15 %) versus 0.85 (85 %). Earlier twin studies (Bailey, J.M., Pillard, R.C. (1991). A genetic study of male sexual orientation. Arch. Gen. Psychiatry. 48(12), 1089–1096) revealed that their concordance for homosexuality in siblings (biological brothers, who are not twins) was lower than in adopted brothers (9.2 % versus 11 %), it contradicting to the idea of genetic determination of same-sex attraction. Moreover, attention is also attracted by the fact that dizygotic male twins demonstrated a significantly higher concordance for homosexuality than siblings (22 % versus 9.2 %). But it is known that dizygotic twins, like siblings, have on an average only 50 % of common genes. If there were genetic determination, such differences would not exist; the revealed difference demonstrates environmental effects, since it is evident that family upbringing of dizygotic twins is much more similar. Also it is necessary to pay attention to the fact that the rate of homosexuality in adopted homosexual brothers (11 %) considerably exceeded recent estimations of the part of homosexuals in the general population and was actually equal to the value for siblings, once again convincingly demonstrating a significant role of the environment in the formation of sexual orientation. We should not also ignore the fact that upbringing of monozygotic twins is even more similar than that of dizygotic ones; this phenomenon can cause their larger concordance for homosexuality.

Genetic factors in anorexia nervosa

1999 ◽  
Vol 14 (4) ◽  
pp. 189-198 ◽  
Author(s):  
A. Kipman ◽  
P. Gorwood ◽  
M.C. Mouren-Siméoni ◽  
J. Adès
Keyword(s):  
Anorexia Nervosa ◽  
Genetic Factors ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Vulnerability Factors ◽  
Adoption Studies ◽  
Complex Disorder ◽  
Dizygotic Twins ◽  
The One ◽  
Familial Environment

SummaryAnorexia nervosa is a severe and complex disorder with incompletely known vulnerability factors. It is generally recognized that anorexia nervosa is a familial disorder, but the majority of twin studies have shown that the concordance rate for monozygotic twins is higher (on average 44%) than for dizygotic twins (on average 12.5%). This difference in concordance rates shows that genetic factors, more than common familial environment, may explain why the `anorexia nervosa' phenotype runs in families. In order to estimate the heritability in the broad sense of anorexia nervosa according to published familial and twin studies, we first assessed the intrapair correlation between monozygotic and dizygotic twins, and secondly calculated the deviation threshold of relatives of affected probands from the relative mean. In this review, we obtained an estimation of the heritability at 0.72 according to all published controlled familial studies (six references quoted in MEDLINE®), and 0.71 for all published twin studies (59 references quoted in MEDLINE®). This estimation is close to the ones previously proposed, between 0.5 and 0.8.Familial and twin studies may also help to define the boundaries of the phenotype, shedding light on the complex relationship between anorexia nervosa on the one hand, and bulimia nervosa, mood disorders, and alcoholism on the other. Demonstrating the importance of genetic factors in anorexia nervosa, and more specifically for anorexia of the restrictive type, requires not only prospective and adoption studies (which are still lacking), but also genetic polymorphisms analyses, which began very recently.

scholarly journals The features of the follicular thyroid cancer genetic determination

2020 ◽  
pp. 100-102
Author(s):  
С.А. Штандель ◽  
В.В. Хазиев ◽  
М.Е. Сазонов
Keyword(s):  
Thyroid Cancer ◽  
Positive Selection ◽  
Genetic Factors ◽  
Complex Analysis ◽  
Cancer Genetic ◽  
Follicular Thyroid Cancer ◽  
Genetic Determination ◽  
Selection Indexes

Комплексный анализ наследственной предрасположенности к фолликулярному раку щитовидной железы (ФРЩЖ) с использованием генеалогического, молекулярно-генетического методов и показателей отбора показал, что ФРЩЖ является генетически самостоятельной формой рака щитовидной железы, описывается параметрами полигенной пороговой модели, в его наследовании существенная роль принадлежит наследственным факторам (88,8%), имеются нелинейные межлокусные взаимодействия, отбор в пользу этой формы заболевания (Δs =0,041) и ассоциация мутаций Р12А и H449H во экзонах 2 и 6 гена PPARγ с фолликулярной структурой неоплазий. The complex analysis of the follicular thyroid cancer (FTC) hereditary predisposition with using of genealogical, molecular methods and selection indexes is shown the FTC genetic independence; the distribution in the population and families may well be described by means of a variants polygene model with the importance role of genetic factors in determination of disease (88,8 %) and have allowed to assume the presence of interloci interactions in system of its genetic control; positive selection (Δs =0,041) of FTC and association of mutations Р12А and H449H in 2 and 6 exons of gene PPARγ with follicular structure of neoplasias.

GENETIC DETERMINATION OF ACUTE DISSEMINATED HISTIOCYTOSIS X (LETTERER-SIWE SYNDROME)

PEDIATRICS ◽  
1970 ◽  
Vol 45 (5) ◽  
pp. 753-765
Author(s):  
Richard C. Juberg ◽  
H. Warner Kloepfer ◽  
Harold A. Oberman
Keyword(s):  
Monozygotic Twins ◽  
Twin Studies ◽  
Recessive Gene ◽  
Histiocytosis X ◽  
Familial Occurrence ◽  
Clinical Impression ◽  
Genetic Determination ◽  
Diffuse Infiltration ◽  
Maculopapular Eruption

Male twins first developed maculopapular eruption of the scalp at 9 months of age and then of other cutaneous areas during the next 3 months. They manifested otorrhea, anemia, and abdominal enlargement at 11 months. They had fever, massive hepatosplenomegaly, and moderate lymphadenopathy when admitted to the hospital at 12 months. There were histiocytes in the skin and bone marrow. The clinical impression of monozygosity was confirmed by several criteria. One twin died at 15 months with diarrhea, and the other twin died at 21 months after developing scattered osteolytic lesions and diabetes insipidus. Autopsy findings in both twins were characteristic of acute disseminated histiocytosis X with diffuse infiltration of nonlipidic histiocytes. An unusual finding was extensive liver involvement in both twins. Evidence for genetic determination of the disease consists of analysis of the literature reports in three categories. Twin studies show three of four pairs of monozygotic twins concordant for the trait. Sibship analysis of the familial occurrence by the a priori method with correction for multiple ascertainment is consistent with the genetic hypothesis. One consanguineous mating has been reported among the seven sibships of familial occurrence. We conclude that at least some instances of this disease result from a single, autosomal, recessive gene with slightly reduced penetrance.

Concordant primary atrophy of the cerebellar granules in monozygotic twins

1954 ◽  
Vol 3 (2) ◽  
pp. 153-162 ◽  
Author(s):  
George A. Jervis
Keyword(s):  
Granular Layer ◽  
Genetic Factors ◽  
Cerebellar Atrophy ◽  
Monozygotic Twins ◽  
Cerebellar Granules

SummaryThe case is described of monozygotic twins similarly affected with a form of cerebellar atrophy characterized by primary lesions of the granular layer. The clinical and pathologic aspects of the disease are briefly discussed and the role of genetic factors in the determination of the condition emphasized.

Phenotypic, genetic, and environmental integration of morphology in a stream population of the threespine stickleback, Gasterosteus aculeatus

1995 ◽  
Vol 52 (6) ◽  
pp. 1307-1317 ◽  
Author(s):  
Jeffrey V. Baumgartner
Keyword(s):  
Natural Selection ◽  
Gasterosteus Aculeatus ◽  
Genetic Factors ◽  
Threespine Stickleback ◽  
Morphometric Traits ◽  
Genetic Determination ◽  
Functional Phenotype ◽  
Pleiotropic Mutation

Phenotypic, genetic, and environmental variances and covariances for 33 morphometric traits were estimated for a population of threespine stickleback, Gasterosteus aculeatus, from the Brush Creek drainage, California, by sib analysis of laboratory-bred families. Heritabilities of the morphometric traits ranged from −0.28 to 0.78, and were moderately low (mean h2 = 0.26); the mean and range of heritabilities for five phenotypic eigenvectors were similar. The average coefficient of genetic determination of the traits and eigenvectors was high (0.57 and 0.63, respectively), indicating a substantial genotypic contribution to variation in body morphology. The defensive complex, a functional set of bony armor structures, was genetically and environmentally integrated: genetic factors (e.g., pleiotropy) are reinforced by environmental factors to produce a functional phenotype. Other components of morphology, including body form, were environmentally, but not genetically, integrated. Given the importance of genetic factors to evolutionary change under natural selection, these results implicate natural selection in the evolution of the defensive complex; the role of natural selection in the evolution of other components of morphology is equivocal. Genetic integration of functionally (phenotypically) independent traits suggests that stochastic processes or pleiotropic mutation also have played a role in the evolution of morphology in this population of sticklebacks.

scholarly journals THE ROLE OF EMBRYONIC GENETIC FACTORS IN THE DEVELOPMENT OF MANIFESTATIONS OF ROSACEA

2020 ◽  
Vol 3 (41) ◽  
Author(s):  
Anas Atalla Salem Sarayreh
Keyword(s):  
Correlation Analysis ◽  
Genetic Factors ◽  
Chromosomal Abnormalities ◽  
Skin Inflammation ◽  
Genetic Determination ◽  
The Face ◽  
Functional Features ◽  
The Subject

The subject of the study – rosacea. The purpose of the work is to determine the embryonic genetic factors that can contribute to the emergence and development of rosacea. The data showing the importance of the genetic determination of the development of the disease in some women with rosacea are presented. Correlation analysis suggests that rosacea-like manifestations on the skin can occur with chromosomal abnormalities during embryogenesis. Embryonic genetic factors affect the distinctive characteristics of the “anatomical patterns” of rosacea (structural and functional features of the skin of the face, blood vessels, and the sebaceous hair complex of this area), the further course of the neurogenic component of the skin inflammation process.Keywords : rosacea, embryonic genetic factors, anatomical patterns.

scholarly journals Co-aggregation and heritability of organ-specific autoimmunity: a population-based twin study

2020 ◽  
Vol 182 (5) ◽  
pp. 473-480 ◽  
Author(s):  
Jakob Skov ◽  
Daniel Eriksson ◽  
Ralf Kuja-Halkola ◽  
Jonas Höijer ◽  
Soffia Gudbjörnsdottir ◽  
...  
Keyword(s):  
Autoimmune Diseases ◽  
Atrophic Gastritis ◽  
Genetic Factors ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Addison’S Disease ◽  
Addison's Disease ◽  
Graves Disease ◽  
Dizygotic Twins ◽  
Organ Specific

Objective Co-aggregation of autoimmune diseases is common, suggesting partly shared etiologies. Genetic factors are believed to be important, but objective measures of environmental vs heritable influences on co-aggregation are absent. With a novel approach to twin studies, we aimed at estimating heritability and genetic overlap in seven organ-specific autoimmune diseases. Design Prospective twin cohort study. Methods We used a cohort of 110 814 twins to examine co-aggregation and heritability of Hashimoto’s thyroiditis, atrophic gastritis, celiac disease, Graves’ disease, type 1 diabetes, vitiligo and Addison’s disease. Hazard ratios (HR) were calculated for twins developing the same or different disease as compared to their co-twin. The differences between monozygotic and dizygotic twin pairs were used to estimate the genetic influence on co-aggregation. Heritability for individual disorders was calculated using structural equational modeling adjusting for censoring and truncation of data. Results Co-aggregation was more pronounced in monozygotic twins (median HR: 3.2, range: 2.2–9.2) than in dizygotic twins (median HR: 2.4, range: 1.1–10.0). Heritability was moderate for atrophic gastritis (0.38, 95% CI: 0.23–0.53) but high for all other diseases, ranging from 0.60 (95% CI: 0.49–0.71) for Graves’ disease to 0.97 (95% CI: 0.91–1.00) for Addison’s disease. Conclusions Overall, co-aggregation was more pronounced in monozygotic than in dizygotic twins, suggesting that disease overlap is largely attributable to genetic factors. Co-aggregation was common, and twins faced up to a ten-fold risk of developing diseases not present in their co-twin. Our results validate and refine previous heritability estimates based on smaller twin cohorts.

Has the “Equal Environments” Assumption Been Tested in Twin Studies?

Twin Research ◽  
2003 ◽  
Vol 6 (6) ◽  
pp. 486-489 ◽  
Author(s):  
Lindon Eaves ◽  
Debra Foley ◽  
Judy Silberg
Keyword(s):  
Genetic Factors ◽  
Twin Studies ◽  
Shared Environment ◽  
Environment Interaction ◽  
Genotype X Environment ◽  
Dizygotic Twins ◽  
Equal Environments Assumption ◽  
Twin Method ◽  
Equal Environments

AbstractArecurring criticism of the twin method for quantifying genetic and environmental components of human differences is the necessity of the so-called “equal environments assumption” (EEA) (i.e., that monozygotic and dizygotic twins experience equally correlated environments). It has been proposed to test the EEA by stratifying twin correlations by indices of the amount of shared environment. However, relevant environments may also be influenced by genetic differences. We present a model for the role of genetic factors in niche selection by twins that may account for variation in indices of the shared twin environment (e.g., contact between members of twin pairs). Simulations reveal that stratification of twin correlations by amount of contact can yield spurious evidence of large shared environmental effects in some strata and even give false indications of genotype x environment interaction. The stratification approach to testing the equal environments assumption may be misleading and the results of such tests may actually be consistent with a simpler theory of the role of genetic factors in niche selection.

Epigenetic factors and molecular markers of the risk of early pregnancy losses

GYNECOLOGY ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 9-16
Author(s):  
Nataly I Frolova ◽  
Tatiana E Belokrinitskaya
Keyword(s):  
Early Pregnancy ◽  
Genetic Factors ◽  
Molecular Genetic ◽  
Pregnancy Complication ◽  
Common Complication ◽  
Epigenetic Factors ◽  
Genetic Determination ◽  
Periconceptional Period ◽  
Combined Impact

Background. Miscarriage is a common complication in early pregnancy. Current studies have shown a higher prevalence of miscarriage, ranging from 10 to 20%. The review is devoted to modern concepts of etiology and pathogenesis of early pregnancy losses. Aim. Assess the role of epigenetic factors and molecular-genetic markers in the pathogenesis and prediction of early pregnancy losses Materials and methods. In order to write this review domestic and foreign publications were searched in Russian and international search systems (PubMed, eLibrary, etc.) for the last 10-15 years. Relevant articles from the peer-reviewed literature and clinical practice guidelines were included. Results. Many recent studies have proved the contribution of various epigenetic factors to the pathogenesis of spontaneous miscarriages, and the molecular-genetic determination such kinds of pregnancy complication has been confirmed. Conclusion. The miscarriage in early gestation is driven by combined impact of epigenetic and molecular-genetic factors, as well as the presence of intergenic interactions. It is may lead to deterioration of physiological functions, and maternal pathologenic pathways could be changed as during her periconceptional period as so during the pregnancy.

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