The Heritability of Life Events: An Adolescent Twin and Adoption Study

2008 ◽  
Vol 11 (3) ◽  
pp. 257-265 ◽  
Author(s):  
Heather R. Bemmels ◽  
S. Alexandra Burt ◽  
Lisa N. Legrand ◽  
William G. Iacono ◽  
Matt McGue
Keyword(s):  
Life Events ◽  
Environmental Effects ◽  
Twin Studies ◽  
Specific Effect ◽  
Genetic Effects ◽  
Adolescent And Young Adult ◽  
Adoption Study ◽  
Independent Events ◽  
Biometrical Models ◽  
Additive Genetic Effects

AbstractAlthough life events are often conceptualized as reflecting exogenous risk factors for psychopathology, twin studies have suggested they are heritable. We undertook a mixed twin/adoption study to further explore genetic and environmental contributions to individual differences in the experience of life events. Specifically, a sample of 618 pairs of like-sex adolescent twins, 244 pairs of like-sex adopted adolescent and young adult siblings, and 128 pairs of like-sex biological siblings completed a life events interview. Events were classified as independent (not likely to have been influenced by respondent's behavior), dependent (likely to have been influenced by respondent's behavior), or familial (experienced by a family member), and then summed to form three life event scales. Variance on the scales was assumed to be a function of four factors: additive genetic effects (a2), shared environmental effects (c2), twin-specific effects (t2), and nonshared environmental effects (e2). Data were analyzed using standard biometrical models. Shared environmental effects were found to be the largest contributor to variance in familial events (c2 = .71; 95% confidence interval of .65, .76); additive genetic effects were the largest contributor to dependent events (a2 = .45; CI = .31, .58); and nonshared environmental effects were found to be the largest contributor independent events (e2 = .57; CI = .51, .64). A significant twin-specific effect was also found for independent life events, indicating that twins are more likely to be exposed to such events than non-twin biological siblings. Findings are discussed in terms of their implication for understanding the nature of psychosocial risk.

scholarly journals Twin Analyses of Fatigue

2007 ◽  
Vol 10 (5) ◽  
pp. 729-733 ◽  
Author(s):  
Ellen Schur ◽  
Niloofar Afari ◽  
Jack Goldberg ◽  
Dedra Buchwald ◽  
Patrick F. Sullivan
Keyword(s):  
Environmental Effects ◽  
Structural Equation ◽  
Environmental Influences ◽  
Twin Studies ◽  
Chronic Fatigue ◽  
Genetic Effects ◽  
Fatigue Syndrome ◽  
Prolonged Fatigue ◽  
The University ◽  
Twin Modeling

AbstractProlonged fatigue equal to or greater than 1 month duration and chronic fatigue equal to or greater than 6 months duration are both commonly seen in clinical practice, yet little is known about the etiology or epidemiology of either symptom. Chronic fatigue syndrome (CFS), while rarer, presents similar challenges in determining cause and epidemiology. Twin studies can be useful in elucidating genetic and environmental influences on fatigue and CFS. The goal of this article was to use biometrical structural equation twin modeling to examine genetic and environmental influences on fatigue, and to investigate whether these influences varied by gender. A total of 1042 monozygotic (MZ) twin pairs and 828 dizygotic (DZ) twin pairs who had completed the University of Washington Twin Registry survey were assessed for three fatigue-related variables: prolonged fatigue, chronic fatigue, and CFS. Structural equation twin modeling was used to determine the relative contributions of additive genetic effects, shared environmental effects, and individual-specific environmental effects to the 3 fatigue conditions. In women, tetrachoric correlations were similar for MZ and DZ pairs for prolonged and chronic fatigue, but not for CFS. In men, however, the correlations for prolonged and chronic fatigue were higher in MZ pairs than in DZ pairs. About half the variance for both prolonged and chronic fatigue in males was due to genetic effects, and half due to individual-specific environmental effects. For females, most variance was due to individual environmental effects.

A Genetic Analysis of Taste Threshold for Phenylthiocarbamide

1981 ◽  
Vol 30 (1) ◽  
pp. 51-57 ◽  
Author(s):  
C. C. Morton ◽  
R. M. Cantor ◽  
L. A. Corey ◽  
W. E. Nance
Keyword(s):  
Genetic Analysis ◽  
Maternal Effects ◽  
Environmental Effects ◽  
Environmental Parameters ◽  
Genetic Effects ◽  
Broad Sense Heritability ◽  
Taste Threshold ◽  
Confidence Levels ◽  
Jackknife Procedure ◽  
Additive Genetic Effects

Taste threshold for phenylthiocarbamide (PTC) was measured in 393 offspring from the families of 85 monozygotic (MZ) twin pairs. PTC scores were bimodally distributed with modes at one and eight and the antimode at five. Because of the non-normality of the distribution, a jackknife procedure was used to obtain 95% confidence intervals for the estimates of genetic, maternal, and environmental parameters. Analyses which assumed no epistasis and which included additive genetic effects revealed that 37.9% of the observed variation in PTC threshold was due to additive genetic effects, 16.6% was due to dominance effects, 14.2% was due to maternal effects, 13.7% was due to a common sibship environment, and 17.6% was due to random environmental effects, yielding a broad sense heritability of 0.55 for the threshold ability to taste PTC. Analyses which did not include additive genetic effects revealed 26.6% of the observed variance was due to dominance effects, 23.6% to maternal effects, and 49.8% to environmental effects at the 0.67 confidence levels, but that environmental factors accounted for 72.4% and dominance effects for 23.6% of the observed variation at the 95% level.

565. A study of variation in twin cattle: III. Growth

1955 ◽  
Vol 22 (1) ◽  
pp. 1-9 ◽  
Author(s):  
J. W. B. King ◽  
H. P. Donald
Keyword(s):  
Environmental Effects ◽  
Live Weight ◽  
Genetic Effects ◽  
Point Of View ◽  
Environmental Variance ◽  
Simple Assumption ◽  
Polynomial Coefficients ◽  
Straight Line ◽  
Best Fitting ◽  
Additive Genetic Effects

1. Polynomial coefficients have been fitted to data on growth in live weight to 19 months and on height at withers to 27 months of age shown by one-egg (MZ) and two-egg (DZ) twins and pairs of half-sisters (HZ). The coefficients obtained (a0, a2 and a3) have been subjected to analysis of variance.2. For growth in live weight, the ratio of intrapair variances for MZ, DZ and HZ pairs was 1:6·8:10 for a1, which gives the straight line best fitting the observed curve. Unrelated pairs, it is calculated, would have had an intrapair variance 20·9 times as great as MZ pairs. From the point of view of minimizing the intrapair variance, the advantage of the MZ pairs was usually a little less for a0, and considerably less for a2 and a3.3. For height at withers, the results were similar to those for weight.4. The contribution of environmental variance to total intrapair variance increased from a0 to a3, while that due to additive genetic effects diminished. Owing to the wide fiducial limits applicable, the results can be accommodated assuming only additive genetic effects in addition to environmental effects as estimated from one-egg twins. The extent to which HZ pairs exceeded the variance expected, however, suggests that this simple assumption may prove inadequate.

Evidence for Nonadditive Genetic Effects on Eysenck Personality Scales in South Korean Twins

2007 ◽  
Vol 10 (2) ◽  
pp. 373-378 ◽  
Author(s):  
Yoon-Mi Hur
Keyword(s):  
Personality Traits ◽  
Model Fitting ◽  
Twin Studies ◽  
Mail Survey ◽  
Monozygotic Twin ◽  
Genetic Effects ◽  
Adolescent And Young Adult ◽  
The South ◽  
South Korean ◽  
Asian Populations

AbstractWhile evidence supporting for nonadditive genetic influences on personality traits in Caucasian populations has been growing in recent years, twin studies that explored the existence of genetic nonadditivity in personality variation in Asian populations are still lacking. Seven hundred and sixty-five pairs of adolescent and young adult twins registered with the South Korean Twin Registry completed the 7 scales of the Eysenck Personality Scales through a mail survey. Maximum likelihood twin correlations were computed and model-fitting analyses were conducted. Monozygotic twin correlations were consistently higher than twice the dizygotic twin correlations for all 7 scales, suggesting pervasive influences of nonadditive genetic effects on personality traits in the South Korean population. Model-fitting analyses indicated that genetic nonadditivity is particularly important for the variation of Impulsivity, Venturesomeness, Empathy, Lie, and Psychoticism. According to the best fitting models, nonadditive genetic effects ranged from 34 to 49% for these scales. For Neuroticism and Extraversion, models that included an additive genetic component fit better than those including a nonadditive genetic variance component.

scholarly journals Genetic analysis of milk yield, fat and protein content in Holstein dairy cows in Iran: Legendre

2013 ◽  
Vol 56 (1) ◽  
pp. 497-508
Author(s):  
R. Abdullahpour ◽  
M. M. Shahrbabak ◽  
A. Nejati-Javaremi ◽  
R. V. Torshizi ◽  
R. Mrode
Keyword(s):  
Protein Content ◽  
Milk Yield ◽  
Environmental Effects ◽  
Milk Fat ◽  
Legendre Polynomials ◽  
Fat Content ◽  
Genetic Effects ◽  
Residual Variance ◽  
Genetic Trend ◽  
Additive Genetic Effects

Abstract. Data including 219 105 test day records of 22 569 first parity Holstein cows in 56 herds were analysed for milk yield, fat content and protein content. Legendre polynomials were used in a random regression model to explain traits curves, additive genetic and permanent environmental effects along days in milk (DIM). Legendre polynomials of order 3 were used to describe additive genetic effects on the traits. For permanent environmental effects, for milk the order of 6 and for fat and protein content the order of 4 were used. Heterogeneity of residual variance was considered. Restricted maximum likelihood (REML) methodology was used to estimate the required parameters. Variations in genetic, permanent environment and residual effects and heritability changes along DIM were computed and illustrated. Daily heritability estimates averaged as 0.22, 0.14 and 0.23 for milk, fat and protein contents, respectively. Minimum correlations between DIM for additive genetic effects were as 0.49, −0.01 and 0.34 for milk, fat and protein contents. There were higher genetic correlations between test day milk yield and protein content compared to fat content. The genetic trend of milk yield has increased over the years from 1971 to 2005, while the genetic trend for fat and protein content declined.

Twin analyses of chronic fatigue in a Swedish national sample

2005 ◽  
Vol 35 (9) ◽  
pp. 1327-1336 ◽  
Author(s):  
PATRICK F. SULLIVAN ◽  
BIRGITTA EVENGÅRD ◽  
ANDREAS JACKS ◽  
NANCY L. PEDERSEN
Keyword(s):  
Environmental Effects ◽  
Complex Traits ◽  
Structural Equation ◽  
Twin Studies ◽  
Complex Trait ◽  
Chronic Fatigue ◽  
National Sample ◽  
Specific Effects ◽  
Definition Of ◽  
Additive Genetic Effects

Background. Chronic fatigue has infrequently been studied in twins. Data from twin studies can inform clinical and research approaches to the management and etiology of human complex traits.Method. The authors obtained telephone interview data on current chronic fatigue from 31406 individuals twins in the Swedish Twin Registry (aged 42–64 years, 75·68% response rate), from both members of 12407 pairs and from one member of 6592 pairs. Of the complete pairs, 3269 pairs were monozygotic, 9010 pairs dizygotic, and 128 pairs of unknown zygosity. Structural equation twin modeling was used to estimate the latent genetic architecture of varying definitions of fatiguing illness.Results. Estimates of additive genetic effects, shared environmental effects, and individual-specific environmental effects were similar in males and females. No definition of current fatiguing illness (ranging from any fatigue to CFS-like illness) was strikingly distinctive. Individual-specific effects were the predominant source of variation, followed by modest genetic influences. We could not exclude a small but conceptually important contribution of shared environmental effects.Conclusions. Current fatiguing illness appears to be a complex trait resulting from both environmental and genetic sources of variation without pronounced differences by gender.

Assessing gene–environment interactions on anxiety symptom subtypes across childhood and adolescence

2007 ◽  
Vol 19 (4) ◽  
pp. 1129-1146 ◽  
Author(s):  
Jennifer Y. F. Lau ◽  
Alice M. Gregory ◽  
Michelle A. Goldwin ◽  
Daniel S. Pine ◽  
Thalia C. Eley
Keyword(s):  
Life Events ◽  
Environmental Effects ◽  
Separation Anxiety ◽  
Negative Life Events ◽  
Child And Adolescent ◽  
Genetic Effects ◽  
Anxiety Symptoms ◽  
Environment Interaction ◽  
Gene Environment Interaction ◽  
Gene Environment

AbstractConsistent evidence shows both genetic and stress-related risks on child and adolescent anxiety, yet few studies have considered the degree to which genetic effects are moderated by stress (gene–environment interaction). We used longitudinal data from both a child and adolescent sample of twins to examine three novel issues on the presence of gene–environment interaction on anxiety symptoms. First, we assessed moderation of genetic risks on anxiety symptoms by negative life events in each age group. Second, by distinguishing between “stable” and “age-specific” genetic factors, we explored the continuity of gene–environment interaction across time and/or its emergence at specific ages. Third, we compared the presence of gene–environment interaction across different symptom types (general, panic, social, and separation). Genetic effects on separation anxiety symptoms in childhood (mean age = 8 years, 6 months) and panic anxiety symptoms in adolescence (mean age = 15 years) increased across independent negative life events. Shared environmental effects on separation anxiety symptoms and nonshared environmental effects on general anxiety symptoms in adolescence were also moderated by negative life events. We interpret these preliminary findings tentatively in the context of gene–environment interaction on anxiety in general, and on early separation and later panic anxiety in particular.

Genetic and maternal effects on juvenile survival and fitness-related traits in three populations of Atlantic salmon

2015 ◽  
Vol 72 (5) ◽  
pp. 751-758 ◽  
Author(s):  
Aimee Lee S. Houde ◽  
Craig A. Black ◽  
Chris C. Wilson ◽  
Trevor E. Pitcher ◽  
Bryan D. Neff
Keyword(s):  
Atlantic Salmon ◽  
Maternal Effects ◽  
Environmental Effects ◽  
Genetic Architecture ◽  
Life Stage ◽  
Random Mating ◽  
Genetic Effects ◽  
Phenotypic Variance ◽  
Offspring Performance ◽  
Additive Genetic Effects

Although studies addressing natural selection have primarily focused on additive genetic effects because of their direct relationship with responses to selection, nonadditive genetic and maternal effects can also significantly influence phenotypes. We partitioned the phenotypic variance of survival and fitness-related traits in juvenile Atlantic salmon (Salmo salar) from three allopatric populations (LaHave, Sebago, and Saint-Jean) into additive genetic, nonadditive genetic, and maternal environmental effects using a full-factorial breeding design. We also modelled the potential increase in offspring performance if nonrandom mating (e.g., mate choice) is considered instead of random mating. The three populations exhibited significant differences in trait values as well as the genetic architecture of the traits. Nevertheless, nonadditive genetic and maternal environmental effects tended to be larger than the additive genetic effects. There was also a shift from maternal environmental to genetic effects during development in two of the populations. That is, maternal environmental effects were larger at early (egg and alevin) life stages, whereas nonadditive effects were larger at the later (fry) life stage. The amount of additive genetic effects was small, suggesting the traits will respond slowly to selection. We discuss how different maternal environmental effects across years may influence the genetic architecture of offspring traits.

scholarly journals Genetic and environmental influences of surfactant protein D serum levels

2006 ◽  
Vol 290 (5) ◽  
pp. L1010-L1017 ◽  
Author(s):  
Grith L. Sørensen ◽  
Jacob v. B. Hjelmborg ◽  
Kirsten O. Kyvik ◽  
Mogens Fenger ◽  
Anette Høj ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Smoking Status ◽  
Adult Population ◽  
Intraclass Correlation ◽  
Serum Levels ◽  
Surfactant Protein ◽  
Genetic Effects ◽  
Surfactant Protein D ◽  
Disease States ◽  
Additive Genetic Effects

The collectin surfactant protein D (SP-D) is an important component of the pulmonary innate immune system, but SP-D is also present on extrapulmonary epithelial surfaces and in serum, where it has been used as a biomarker for pulmonary disease states. In this study, we investigate the mechanisms defining the constitutional serum level of SP-D and determine the magnitude of the genetic contribution to serum SP-D in the adult population. Recent studies have demonstrated that serum SP-D concentrations in children are genetically determined and that a single nucleotide polymorphism (SNP) located in the NH2-terminal region (Met11Thr) of the mature protein is significantly associated with the serum SP-D levels. A classic twin study was performed on a twin population including 1,476 self-reported healthy adults. The serum SP-D levels increased with male sex, age, and smoking status. The intraclass correlation was significantly higher for monozygotic (MZ) twin pairs than for dizygotic (DZ) twin pairs. Serum SP-D variance was influenced by nonshared environmental effects and additive genetic effects. Multivariate analysis of MZ and DZ covariance matrixes showed significant genetic correlation among serum SP-D and metabolic variables. The Met11Thr variant explained a significant part of the heritability indicating that serum SP-D variance could be decomposed into non-shared environmental effects (e2 = 0.19), additive genetic effects (h2 = 0.42), and the effect of the Met11Thr variations (q2 = 0.39).

Combining Ability of Plant Height and Yield components in Indian Mustard (Brassica junceaL.Czern & Coss.) under Salt affected Soil using Line×Tester Analysis

2016 ◽  
Vol 3 (2) ◽  
Author(s):  
SHAILESH CHAND GAUTAM ◽  
MP Chauhan
Keyword(s):  
Plant Height ◽  
Seed Yield ◽  
Combining Ability ◽  
Yield Components ◽  
Indian Mustard ◽  
Heritability Estimate ◽  
Genetic Effects ◽  
Narrow Sense ◽  
Narrow Sense Heritability ◽  
Additive Genetic Effects

Line × tester analysis of twenty lines and three testers of Indian mustard (Brassica juncea L. Czern & Coss.) cultivars were used to estimate general combining ability (GCA), specific combining ability (SCA) effects, high parent heterosis and narrow-sense heritability estimate for plant height, yield components and seed yield. Significant variance of line x tester for the traits like pods per plant and seed yield indicating non additive genetic effects have important role for controlling these traits. Significant mean squares of parents v/s crosses which are indicating significant average heterosis were also significant for all the traits except seeds per pod. High narrow-sense heritability estimates for all the traits except seeds per pod exhibited the prime importance of additive genetic effects for these traits except seeds per pod. Most of the crosses with negative SCA effect for plant height had at least one parent with significant negative or negative GCA effect for this trait. For most of the traits except pods per plant, the efficiency of high parent heterosis effect was more than SCA effect for determining superior cross combinations.

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