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Gene-environment correlation (or genotype-environment correlation) is said to occur when exposure to environmental conditions depends on an individual's genotype. ==Definition== Gene-environment correlations (or rGE) can arise by both causal and non-causal mechanisms. Of principal interest are those causal mechanisms which indicate genetic control over environmental exposure. Genetic variants influence environmental exposure indirectly via behavior. Three causal mechanisms giving rise to gene-environment correlations have been described. : (i) Passive gene-environment correlation refers to the association between the genotype a child inherits from his or her parents and the environment in which the child is raised. Parents create a home environment that is influenced by their own heritable characteristics. Biological parents also pass on genetic material to their children. When the children's genotype also influences their behavioral or cognitive outcomes, the result can be a spurious relationship between environment and outcome. For example, because parents who have histories of antisocial behavior (which is moderately heritable) are at elevated risk of abusing their children, a case can be made for saying that maltreatment may be a marker for genetic risk that parents transmit to children rather than a causal risk factor for children’s conduct problems. : (ii) Evocative (or reactive) gene-environment correlation happens when an individual's (heritable) behavior evokes an environmental response. For example, the association between marital conflict and depression may reflect the tensions that arise when engaging with a depressed spouse rather than a causal effect of marital conflict on risk for depression. : (iii) Active gene-environment correlation occurs when an individual possesses a heritable propensity to select environmental exposure. For example, individuals who are characteristically extroverted may seek out very different social environments than those who are shy and withdrawn. Gene-environment correlation can also arise from non-causal mechanisms, including evolutionary processes and behavioral 'contamination' of the environmental measure. Evolutionary processes, such as genetic drift and natural selection, can cause allele frequencies to differ between populations. For example, exposure to malaria-bearing mosquitoes over many generations may have caused the higher allele frequency among certain ethnic groups for the sickle hemoglobin (HbS) allele, a recessive mutation that causes sickle-cell disease but confers resistance against malaria. In this way, HbS genotype has become associated with the malarial environment. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gene-environment correlation」の詳細全文を読む スポンサード リンク
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