Using MZ Twins in Experimental Research to Test for the Presence of a Genotype-Environment Interaction Effect

1990 ◽  
Vol 39 (1) ◽  
pp. 85-89 ◽  
Author(s):  
C. Bouchard ◽  
L. Pérusse ◽  
C. Leblanc
Keyword(s):  
Treatment Effect ◽  
Repeated Measures ◽  
Intraclass Correlation ◽  
Experimental Treatment ◽  
Biological Traits ◽  
Environment Interaction ◽  
Genotype Environment Interaction ◽  
Mz Twins ◽  
Environment Interaction Effect

AbstractDespite some evidence that genotype-environment interaction (G×E) effects may be involved in the variation observed in behavioral and biological traits, few attempts have been made to detect and quantify this component of genetic variation in humans. We propose that one way to achieve this goal is to challenge several genotypes in a similar manner, submitting both members of several MZ twin pairs to an ethically acceptable experimental treatment capable of inducing an adaptative response. In this situation, the G×E effect can be assessed with a two-way analysis of variance for repeated measures on one factor, the treatment effect. In this design, twins are considered nested within the pair, whereas the treatment effect is considered a fixed variable. The intrapair resemblance in the response to the treatment is quantified with an intraclass correlation coefficient computed with between-sibhips and within-sibhips means of squares. To illustrate this approach, changes induced by long-term endurance training were studied in 10 MZ twin pairs. Significant intrapair resemblance in the response of maximal oxygen uptake was observed, with about 7 to 8 times more variance between pairs than within pairs. This design with MZ twins may be helpful in the study of human variation for multifactorial phenotypes.

Twin Study on Myopia

1987 ◽  
Vol 36 (4) ◽  
pp. 535-540 ◽  
Author(s):  
L.L.-K. Lin ◽  
C.-J. Chen
Keyword(s):  
Intraclass Correlation ◽  
Correlation Coefficients ◽  
Environment Interaction ◽  
Ophthalmological Examination ◽  
Genetic Determination ◽  
Intraclass Correlation Coefficients ◽  
Gene Environment Interaction ◽  
Gene Environment ◽  
Genetic And Environmental Factors ◽  
Mz Twins

AbstractIn order to reassess the relative importance of genetic and environmental factors in the development of myopia in Chinese schoolchildren, 90 pairs of MZ and 36 pairs of like-sex DZ twins were enrolled for detailed ophthalmological examination about their ocular refractions. Corneal curvatures and axial lengths were also measured. With equivalent settings of the range for concordance, corneal curvatures showed higher concordance rate (84%) than ocular refractions (65%) and axial lenghts (59%) in MZ twins. F-test on the intrapair variances between MZ and DZ twins revealed a significant hereditary role in determining the ocular refraction and its optical components. The degree of genetic determination was expressed by heritability indices, which were derived from intraclass correlation coefficients. The diversity of sample ages and refractions, while making the obtained data difficult to further explore the gene-environment interaction, led to the observation of more intrapair differences with age and myopic progression in MZ twins.

scholarly journals Stability Analysis of Genotype × Environment Interaction Effect on Sugar Yield in Sugar Beet Hybrids

2019 ◽  
Vol 11 (32) ◽  
pp. 33-40
Author(s):  
Parviz Fasahat ◽  
Samar Khayamim ◽  
Jamshid Soltani Idliki ◽  
Saeed Darabi ◽  
Adel Pedram ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Sugar Beet ◽  
Interaction Effect ◽  
Sugar Yield ◽  
Environment Interaction ◽  
Genotype Environment Interaction ◽  
Environment Interaction Effect

scholarly journals Causal inference for long-term survival in randomised trials with treatment switching: Should re-censoring be applied when estimating counterfactual survival times?

2018 ◽  
Vol 28 (8) ◽  
pp. 2475-2493 ◽  
Author(s):  
NR Latimer ◽  
IR White ◽  
KR Abrams ◽  
U Siebert
Keyword(s):  
Treatment Effect ◽  
Failure Time ◽  
Survival Function ◽  
Experimental Treatment ◽  
Control Group ◽  
Survival Times ◽  
Term Survival ◽  
Long Term Survival ◽  
Treatment Switching

Treatment switching often has a crucial impact on estimates of effectiveness and cost-effectiveness of new oncology treatments. Rank preserving structural failure time models (RPSFTM) and two-stage estimation (TSE) methods estimate ‘counterfactual’ (i.e. had there been no switching) survival times and incorporate re-censoring to guard against informative censoring in the counterfactual dataset. However, re-censoring causes a loss of longer term survival information which is problematic when estimates of long-term survival effects are required, as is often the case for health technology assessment decision making. We present a simulation study designed to investigate applications of the RPSFTM and TSE with and without re-censoring, to determine whether re-censoring should always be recommended within adjustment analyses. We investigate a context where switching is from the control group onto the experimental treatment in scenarios with varying switch proportions, treatment effect sizes, treatment effect changes over time, survival function shapes, disease severity and switcher prognosis. Methods were assessed according to their estimation of control group restricted mean survival that would be observed in the absence of switching, up to the end of trial follow-up. We found that analyses which re-censored usually produced negative bias (i.e. underestimating control group restricted mean survival and overestimating the treatment effect), whereas analyses that did not re-censor consistently produced positive bias which was often smaller in magnitude than the bias associated with re-censored analyses, particularly when the treatment effect was high and the switching proportion was low. The RPSFTM with re-censoring generally resulted in increased bias compared to the other methods. We believe that analyses should be conducted with and without re-censoring, as this may provide decision-makers with useful information on where the true treatment effect is likely to lie. Incorporating re-censoring should not always represent the default approach when the objective is to estimate long-term survival times and treatment effects.

scholarly journals Diet-Induced Plasticity of Linear Static Allometry Is Not So Simple for Grasshoppers: Genotype–Environment Interaction in Ontogeny Is Masked by Convergent Growth

2019 ◽  
Vol 59 (5) ◽  
pp. 1382-1398 ◽  
Author(s):  
Daniel B Thompson
Keyword(s):  
Genetic Variation ◽  
Repeated Measures ◽  
Graphical Model ◽  
Fourth Instar ◽  
Coarse Grained ◽  
Environment Interaction ◽  
Leg Length ◽  
Genotype Environment Interaction ◽  
High Nutrient ◽  
Static Allometry

Abstract Grasshoppers, Melanoplus sanguinipes (Orthoptera: Acrididae), develop larger head width (HW) and shorter leg length, relative to body size, when fed low nutrient, lignin-rich grasses compared to sibs fed a diet of high nutrient grasses. To elucidate how underlying genetic variation and plasticity of growth generate plasticity of this linear static allometry within coarse-grained environments, I measured head and leg size of three nymphal instars and adult grasshoppers raised on either a low or high nutrient diet within a half-sib quantitative genetic experiment. Doubly-multivariate repeated measures multiple analysis of variance (MANOVA) of head, mandible, and hind leg size and their rate of growth (mm/period) and growth period (days) through ontogeny were used to analyze how the ontogeny of diet-induced plasticity for these variables and additive genetic variation for plasticity (genotype × environment interaction [G×E]) contribute to plasticity in functional linear static allometry. Genetic variation for diet-induced plasticity (G×E) of head and leg size varied through ontogeny, as did genetic variation for plasticity of growth in third and fourth instar nymphs. Despite extensive genetic variation in plasticity of HW and leg length in fourth instar nymphs, the static allometry between head and leg was stable within each diet because the patterns of G×E were similar for HW, leg length and their coordinated growth. Nutrient sensitive plasticity in growth shifted the intercept but not the slope of static allometry, a result consistent with one outcome of a graphical model of the relationships between G× E and plasticity of within environment static allometry. In addition, G×E of fourth instar head and leg size was reduced in adults by negatively size-dependent, convergent growth in the last period of ontogeny. Consequently, the bivariate reaction norms of head and leg size for adults exhibited no G×E and, again, plasticity in the intercept but not in the slope of static allometry. The ontogeny of seemingly simple diet-induced linear static allometry between functional body parts in grasshoppers arises from a complex combination of differing patterns of nutrient-sensitive growth, duration of growth, convergent growth, and G×E, all relevant to understanding the development and evolution of functional allometry in hemimetabolous insects.

scholarly journals Stem breakage and forking in low and high elevation Pinus tecunumanii

2011 ◽  
Vol 60 (1-6) ◽  
pp. 1-8
Author(s):  
B. I. Nyoka ◽  
P. Tongoona ◽  
C. M. Gumbie
Keyword(s):  
Test Site ◽  
High Elevation ◽  
Seed Source ◽  
Environment Interaction ◽  
Source Selection ◽  
Genotype Environment Interaction ◽  
Stem Breakage ◽  
Pinus Tecunumanii ◽  
The Mean

Summary The incidences of stem breakage and forking at ages five and eight years in low and high elevation Pinus tecunumanii were assessed in multilocation provenance-progeny tests comprising 16 provenances of both low and high elevation P. tecunumanii. Stem breakage and forking were found to be more severe at the highest test site (1760m a.s.l.), and progressively declined with decreasing altitude. The mean stem breakage at individual sites for the two ages ranged from 0.7% to 19.5% in the low elevation P. tecunumanii, while that of the high elevation P. tecunumanii was between 0% and 12.9%. The mean percent of forked trees ranged between 3.9% and 46.8% in the low elevation P. tecunumanii and from 5.3% to 27.5% in the high elevation P. tecunumanii. The wide provenance variation in stem breakage and forking suggests that genetic factors related to seed source influence these traits. The low elevation P. tecunumanii had significantly higher incidences of stem breakage and forked trees compared to the high elevation P. tecunumanii. Overall, provenances with very low levels of stem breakage and forking included San Jerónimo, Montana Sumpul, Las Piedrecitas and Jocón. Although tested on a limited number of sites, the genotype* environment interaction at both provenance and family level appeared to be inconsequential. The mean percent of trees with stem breakage and forks increased between the two assessment ages, with changes ranging from small to more than double, implying that decision on selection against stem breakage and forking should be avoided at five years or earlier. The results of this study showed that the challenges of stem breakage and forking in plantations can be managed by one or a combination of site and seed source selection, while intensive breeding and selection could also be used as a long term strategy.

Lack of Agreement of Chromogenic and Glotting Assays for Factor X and Protein C in Warfarinised Plasma

1991 ◽  
Vol 65 (04) ◽  
pp. 360-363 ◽  
Author(s):  
P Han ◽  
K P Fung ◽  
U Rahdakrishnan
Keyword(s):  
Serine Proteases ◽  
Protein C ◽  
Warfarin Therapy ◽  
Intraclass Correlation ◽  
Chromogenic Substrate ◽  
Factor X ◽  
Laboratory Automation ◽  
Quantitative Results ◽  
Assay Methods

SummaryCoagulation serine proteases can be measured with either a chromogenic substrate assay or a clotting assay using deficient plasmas. It is a concern whether both assays give similar quantitative results, in particular in plasma obtained fiom patients on long term warfarin therapy. If these two assay methods were interchangeable, then the chromogenic substrate assay has the advantages of precision as well as laboratory automation. We used the intraclass correlation coefficient (r1) to assess the agreement between the two methods in measuring factor X and protein C levels in warfarinised plasma. The results indicate that the extent and pattern of agreement of the two methods for the measurement of the two variables in warfarinised plasma are poor, despite high Pearson product moment coefficients of correlation.

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