Description
One method to investigate gene-environment interactions is to study monozygotic twins.
Identify an example of a twin study not listed in the textbook used to examine the gene-
environment interaction of a specific disease or condition. Briefly summarize the gene-
environment interaction investigated, the methods, and the results. What are other possible
methods for studying gene-environment interactions as they relate to improving population
health?
Gene-environment Interactions
Indeed, the investigation of gene-environment interactions necessitates studying monozygotic
twins with the aim of determining the extent to which phenotypic similarity between individuals
can be predicted by their genetic relatedness without considering their biological level. This
model provides a suitable approach for disentangling effects of genes and environments based on
the assumption that twins who grew up together in the same household are expected to resemble
each other because they are subject to similar influences (Bishop, 2015). These influencing
factors include parental stimulation, diet, schooling, and the prenatal environment in utero. As
such, the investigation of gene-environment interactions determines whether monozygotic twins
are more similar to one another as compared to fraternal twins. For instance, studies of gene-
environment interaction in twin models have necessitated grouping environments to fit multiple
group models to data for people in environment 1 and 2 separately and subsequently testing
whether there were significant differences. These studies have adopted basic structural equation
modeling techniques in determining whether there are significant differences in the importance
of environmental and genetic factors across groups.
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One example that follows the model described above entailed the use of data from the
Australian twin register in testing whether the relative importance of genetic effects on alcohol
consumption varied as a function of marital status. As a result, the study revealed that having a
relationship based on marriage significantly reduced the impact of genetic influences on alcohol
consumption (Barsky & Gaysina, 2016). On the one hand, among the younger sample of twins
involved in the study, genetic liability accounted for approximately half as much variance in
drinking among married women (31%) as among unmarried women (60%). On the other hand, a
parallel effect was identified among adult twins, which indicated that genetic effects accounted
for less than 60% of the variance in married respondents but more than 76% in unmarried
respondents (Barsky & Gaysina, 2016). Seemingly, genetic effects were associated with playing
an integral role in longitudinal drinking patterns from late adolescence to early adulthood among
individuals residing in urban settings while common environmental effects exerted a greater
influence across the same age range among individuals in rural settings.
Most fundamentally, other possible methods for gene-environment interactions as they
relate to improving population health include the determination of genetic correlation between
traits displayed in different environments in situations involving pairs discordant for exposure.
Additionally, the investigation may further involve the adoption of the genome-wide association
method that focuses on the identification of the problems posed by a complex multifactorial
disorder in the determination of the genes affecting the condition (Bishop, 2015). It necessitates
the use of large samples of affected and unaffected individuals and comparing them to find
genetic variants that influence specific traits.
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References
Barsky, P., & Gaysina, D. (2016). Gene-Environment Interplay and Individual Differences in
Psychological Traits. Behavioral Genetics for Education, 24-41.
Bishop, D. V. (2015). The interface between genetics and psychology: lessons from
developmental dyslexia. Proceedings of the Royal Society B: Biological
Sciences, 282(1806), 20143139-20143139.