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 January 2016 Volume 57, Issue 1
Figure 1 Path model for univariate analysis of a twin study. The observed phenotypes of twins 1 and 2 (scores 1 and 2) are represented in squares while latent factors that influence them are represented in circles (A, C, D, E). Additive (A) and dominant (D) genetics are correlated by a factor of 1.0 for MZ twins, and by 0.5 (A) and 0.25 (D), respectively, for DZ twins. Common environment (C) is fully correlated for all twins while unshared environment (E) is uncorrelated. Regression coefficients of the observed variables on the different latent factors are shown in lowercase: h is the regression coefficient of the additive genetic effect. (C, D) cannot be estimated simultaneously. Figure 1 Path model for univariate analysis of a twin study. The observed phenotypes of twins 1 and 2 (scores 1 and 2) are represented in squares while latent factors that influence them are represented in circles (A, C, D, E). Additive (A) and dominant (D) genetics are correlated by a factor of 1.0 for MZ twins, and by 0.5 (A) and 0.25 (D), respectively, for DZ twins. Common environment (C) is fully correlated for all twins while unshared environment (E) is uncorrelated. Regression coefficients of the observed variables on the different latent factors are shown in lowercase: h is the regression coefficient of the additive genetic effect. (C, D) cannot be estimated simultaneously. Figure 2 Average results for optical log(S) (black symbols) psychophysical log(S) (gray symbols) and spherical equivalent (D) of the manifest refraction (white symbols), for twin A plotted against twin B for monozygotic (left graphs) and dizygotic (right graphs) twin pairs. Figure 2 Average results for optical log(S) (black symbols) psychophysical log(S) (gray symbols) and spherical equivalent (D) of the manifest refraction (white symbols), for twin A plotted against twin B for monozygotic (left graphs) and dizygotic (right graphs) twin pairs. Table 1 Pearson Correlation Coefficients for Right Eye (OD)
Versus Left Eye (OS) in MZ and DZ Twin Pairs for all the Variables Considered in This Study; All Statistically Significant at P < 0.001 Table 1 Pearson Correlation Coefficients for Right Eye (OD) Versus Left Eye (OS) in MZ and DZ Twin Pairs for all the Variables Considered in This Study; All Statistically Significant at P < 0.001
Table 2 Intraclass Correlation Coefficients (ICC) and 95% Confidence Intervals (CI95%) for the Logarithm of the Two Straylight Parameters Considered and the
Equivalent Sphere of the Manifest Refraction After Correcting for Age and Sex Effects Table 2 Intraclass Correlation Coefficients (ICC) and 95% Confidence Intervals (CI95%) for the Logarithm of the Two Straylight Parameters Considered and the Equivalent Sphere of the Manifest Refraction After Correcting for Age and Sex Effects
Table 3 Model-Fitting Results for Analysis of Optical and Psychophysical Intraocular Straylight and Refractive Error Table 3 Model-Fitting Results for Analysis of Optical and Psychophysical Intraocular Straylight and Refractive Error
What are genetic and environmental influences?Science tells us that the interactions between genes and environment shape human development. Despite the misconception that genes are “set in stone,” research shows that early experiences can determine how genes are turned on and off — and even whether some are expressed at all.
What is the difference between genetic traits and environmental traits?Inherited traits are the traits you get from your parents through the genes they pass down to you, their offspring. Environmental traits are influenced by your environment. You can learn them or control them.
What is a environmental influence?Environmental influences are hypothesized to influence behavior both indirectly and directly. The indirect causal mechanism reflects the mediating role of behavior-specific cognitions in the influence of the environment on behavior.
What is meant by genetic influence?Genetic influences operate at two levels: one is the genetic predisposition to certain diseases, and the other is the genetic determination of disease. From: International Encyclopedia of the Social & Behavioral Sciences, 2001.
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