4.4 Gene-Environment Interplay
The Human Development Teaching & Learning Group and Meredith Palm
Learning Objectives
- Distinguish between three types of gene-environment correlations
- Identify genotype-environment interactions
- Explain how epigenetics are an example of gene-environment interplay
As you have previously read, behavioral genetics is the scientific study of the interplay between genetic and environmental contributions to behavior. Often referred to as the nature/nurture debate, Gottlieb (1998, 2000, 2002) suggests an analytic framework for this debate that recognizes the interplay between the environment, behavior, and genetic expression. This bidirectional interplay indicates that the environment can affect the expression of genes just as genetic predispositions can impact a person’s potentials. Additionally, environmental circumstances can trigger symptoms of a genetic disorder. For example, a person who has sickle cell anemia, a recessive gene linked disorder, can experience a sickle cell crisis under conditions of oxygen deprivation. Or, someone predisposed genetically to type-two diabetes can trigger the disease through poor diet and little exercise.
Research has shown how the environment and genotype interact in several ways. Genotype-Environment Correlations refer to the processes by which genetic factors contribute to variations in the environment (Plomin et al., 2013). There are three types of genotype-environment correlations:
Passive genotype-environment correlations occur when children passively inherit both the genes and the environments their family provides. Certain behavioral characteristics, such as being athletically inclined, may run in families. Children in these families have inherited both the genes that would enable success at these activities, and an environment that encourages them to engage in sports. Figure 4.8 highlights this correlation by demonstrating how a family passes on water skiing skills through both genetics and environmental opportunities.
Evocative genotype-environment correlations refer to how the social environment reacts to individuals based on their inherited characteristics. For example, whether children have a more outgoing or shy temperament will affect how they are treated by others.
Active genotype-environment correlations occur when individuals seek out environments that support their genetic tendencies. This is also referred to as niche picking. For example, children who are musically inclined seek out music instruction and opportunities that then facilitate their natural musical ability.
Conversely, genotype-environment interactions involve genetic susceptibility to the environment. Adoption studies provide evidence for genotype-environment interactions. For example, the Early Growth and Development Study (Leve et al., 2010) followed 360 adopted children and their adopted and biological parents in a longitudinal study. Results have shown that children whose biological parents exhibited psychopathology, exhibited significantly fewer behavior problems when their adoptive parents used more structured (vs. unstructured) parenting. Additionally, higher levels of psychopathology in adoptive parents increased the risk that children would develop behavior problems, but only when the biological parents’ psychopathology was also high. Consequently, these results show that environmental effects on behavior differ based on the individual’s genotype, especially the effects of stressful environments on genetically at-risk children.
Lastly, the study of epigenetics examines modifications in DNA that affect gene expression and are passed on when the cells divide. Environmental factors, such as nutrition, stress, and teratogens are thought to change gene expression by switching genes on and off. These gene changes can then be inherited by daughter cells. This would explain why monozygotic or identical twins may increasingly differ in gene expression with age. For example, Fraga et al. (2005) found that when examining differences in DNA, a group of monozygotic twins were indistinguishable during the early years. However, when the twins were older there were significant discrepancies in their gene expression, most likely due to different experiences. These differences included a range of personal characteristics, including susceptibilities to disease.
Link to Learning: The Human Genome Project
In 1990 the Human Genome Project (HGP), an international scientific endeavor, began the task of sequencing the 3 billion base pairs that make up the human genome. In April of 2003, more than two years ahead of schedule, scientists gave us the genetic blueprint for building a human. Since then, using this information from the HGP, researchers have discovered the genes involved in over 1800 diseases. In 2005 the HGP amassed a large data base called HapMap that catalogs genetic variations in 11 global populations. Data on genetic variation can improve our understanding of differential risk for disease and reactions to medical treatments, such as drugs. Pharmacogenomic researchers have already developed tests to determine whether a patient will respond favorably to certain drugs used in the treatment of breast cancer, lung cancer, or HIV by using information from HapMap (NIH, 2015).
Future directions for the HGP include identifying the genetic markers for all 50 major forms of cancer (The Cancer Genome Atlas), continuing to create more effective drugs for the treatment of disease, and examining the legal, social and ethical implications of genetic knowledge (NIH, 2015).
From the outset, the HGP established ethical issues one of their main concerns. Part of the HGP’s budget supports research and holds workshops that address these concerns. Who owns this information, and how the availability of genetic information may influence healthcare and its impact on individuals, their families, and the greater community are just some of the many questions being addressed (NIH, 2015).
Conclusions
As you’ve read in this section, there is a genetic component to nearly every human trait, but our genes do not determine every trait we express. The complex relationships between genes and the environment contribute to diversity in our personalities and traits, meaning that even if two individuals are genetically identical (as in the case of monozygotic twins) they will have some differences between them. These complex interactions begin as soon as a genetically unique zygote (or zygotes, in the case of twins) is created at conception. Our next chapter will explore the ways that the prenatal environment begins to shape the course of development.
References (Click to expand)
Fraga, M. F., Ballestar, E., Paz, M. F., Ropero, S., Setien, F., Ballestar, M. L., … Esteller, M. (2005). Epigenetic differences arise during the lifetime of monozygotic twins. Proceedings of the National Academy of Science (USA), 102, 10604-10609. DOI:10.1073/pnas.0500398102
Gottlieb, G. (1998). Normally occurring environmental and behavioral influences on gene activity: From central dogma to probabilistic epigenesis. Psychological Review, 105, 792-802.
Gottlieb, G. (2000). Environmental and behavioral influences on gene activity. Current Directions in Psychological Science, 9, 93-97.
Gottlieb, G. (2002). Individual development and evolution: The genesis of novel behavior. New York: Oxford University Press.
Leve, L. D., Neiderhiser, J. M., Scarmella, L. V., & Reiss, D. (2010). The early growth and development study: Using the prospective adoption design to examine genotype-interplay. Behavior Genetics, 40, 306-314. DOI: 10.1007/s10519-010- 9353-1
National Institute of Health (2015). An overview of the human genome project. Retrieved from http://www.genome.gov/12011238
Plomin, R., DeFries, J. C., Knopik, V. S., & Niederhiser, J. M. (2013). Behavioral genetics (6th edition). NY: Worth Publishers.
Licenses & Attributions (Click to expand)
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- “Lifespan Development: A Psychological Perspective, Second Edition” by Martha Lally and Suzanne Valentine-French is licensed under a CC-BY-NC-SA-3.0
- “Beginnings” by by Human Development Teaching & Learning Group is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Media Attributions
- waterski © Martha Lally and Suzanne Valentine-French is licensed under a CC BY-NC-SA (Attribution NonCommercial ShareAlike) license