Gene-Environment Interaction

Why are some people more prone to falling sick when climate changes while others remain all right even in extreme conditions? Or have you thought about why identical twins differ so much in their personalities? This happens due to the interaction between genes and the environment. This is the popular debate of "nature Vs. nurture".

What does Entails Gene-Environment Interaction?

Gene-environment interactions are instances in which a genotype's impact on illness risk depends on environmental exposure, or vice versa, where a genotype's impact on disease risk depends on the genotype and the environmental exposure. Studies of gene-environment interactions can shed light on the basic causes of disease and may have repercussions for public health. The NAT2 gene, smoking as an environmental component, and bladder cancer are three examples of gene-environment interaction.

A known risk factor for bladder cancer is tobacco use. According to the American Cancer Society, smokers are at least three times more likely than non-smokers to develop bladder cancer. Compared to smokers with a different variation of NAT2, those with one variant have a substantially higher risk of developing bladder cancer. In other words, the risk of bladder cancer is determined by the interaction between the genetic factor—NAT2 variation—and the environmental factor—smoking behavior.

Various Perspectives

Genes do not exist by themselves. Even though we are all biological beings, the environment in which we live has a significant impact on how and when our genes manifest themselves as well as how they are combined. Everyone is the result of a unique interplay between genetics and environment. Following are some perspectives for studying this interaction between genes and the environment−

Range of Reaction

According to the range of reaction theory, our environment influences our genes to determine where in that range we will fall, while our genes set the parameters within which we can function. A person will be more likely to realize their full potential than if she were nurtured in conditions of considerable deprivation, for instance, if her genetic composition predisposes her to high levels of intellectual potential and she is raised in a wealthy, stimulating environment. Genes impose clear boundaries on potential, and the environment controls how much of that potential is fulfilled, according to the range of reaction theory.

Genetic-Environmental Correlation

According to this perspective, genes affect our environment, and our environment affects how our genes are expressed. Our genes and environment interact, as in the range of reactions, and they also have a two-way influence. For instance, a child of an NBA player would likely grow up playing basketball, and the child may be able to reach their maximum genetic and athletic potential due to this exposure. Therefore, the child's environment is well adapted to support the child's genetic potential due to the influence of the parent's genes, which the child also shares.


The study of how the same genotype can be expressed in several ways goes beyond the genotype in the discipline of epigenetics. In other words, scientists investigate how quite distinct phenotypes can result from the same gene. As was already mentioned, the context of the environment frequently affects gene expression in subtle ways. For instance, genetic information is shared by identical twins (identical twins develop from a single fertilized egg that split, so the genetic material is the same in each; in contrast, fraternal twins develop from two different eggs fertilized by different sperm, so the genetic material varies as with non-twin siblings. However, even though twins have the same genes, there is still a huge variation in how gene expression manifests throughout each twin's life.

There are situations when one twin will experience a sickness while the other does not. In one instance, Tiffany's identical twin, who was 7, passed away from cancer, but Tiffany's twin, now 19 years old, has never had the disease. Despite having the same genotype, these people have different phenotypes because of how that genetic information manifests through time. Because the genotype is not fixed and constrained in the epigenetic perspective, it differs greatly from the range of reaction perspective.

Gene-Environment Interaction of Various Attributes

So far, studies have demonstrated that behavior results from how heredity and environment interact, for example, temperament. A persistent aspect of a person's personality, temperament is defined as patterns of arousal and emotionality. According to studies, some kids are more enthusiastic about physical activity from birth than other kids. Further, the opportunity parents give their children may enable some kids to overcome their shyness and be more active. Studies have clearly shown that children who grow up in an environment that is stressful, such as one where there is a marital conflict or a prolonged illness in the family, may continue to be reserved.

Intelligence, personality, and psychological disorders are often studied in psychology due to gene-environmental interactions. In this context, these interactions are often said to reflect multi-factorial transmission. Multi-factorial transmission is reflected in traits determined by genetic and environmental variables. In multi-factorial transmission, the genotype defines the phenotypic range.

Thus, genotype describes the fundamental genetic mix a child inherits from their parents. Phenotypes are genuine, observable traits that result from genetic and environmental factors. For instance, despite having an average genotype for intelligence, an individual's IQ may vary based on the environment they were exposed to. In these situations, the environment controls the phenotypic expression of a particular genotype.

Similarly, not all actions and attributes are influenced by the environment, and it is impossible to assert that environmental or genetic causes only bring on a particular action. Rather, it is the way these factors interact that results in the exhibition of certain traits.

Methods of Study

The techniques used to research the relative importance of genetic and environmental factors are as follows.

Animal Studies

One technique for examining the relative influence of environment and heredity. Animals with similar genetic makeup are bred together to study environmental factors' effects. In this way, it is frequently possible to study the effects of various environmental settings, for example, raising some genetically similar animals in stimulating environments while raising others in relatively deplorable environments. Similarly, by subjecting genetically distinct animals to the same environment, researchers can evaluate the impact of genetic characteristics. Animal studies provide sufficient data to form conclusions, but it still needs to be determined how far these results may be generalized to humans.

Adoption and Twin Studies

Researchers cannot influence a human's genetic or environmental origins. Studying monozygotic twins, or identical twins born from the same fertilized cell, is the best way to understand the interaction between genetics and the environment. Since their genetic makeup is identical, any differences in their behavior must only be caused by external factors. Researchers can use identical twins adopted at birth and raised in various environments to explore the effects of environmental factors.

Family Studies

This is an additional strategy in which individuals who are unrelated but share a similar environment are researched. For instance, a family adopting two young, unrelated children will typically give them a comparable setting. Similar environmental circumstances can be used to explain the similarities shown in these kids. When a certain trait has a strong association between a child's biological parents and them and a weaker association between a child's adoptive parents and them, there is sufficient evidence to support the importance of the genetic factor in determining the trait and vice versa. This is done by developmental psychologists who study people based on their degree of genetic similarity.


Genes do not alone determine the characteristics of individuals; rather, the environment plays an important role too. However, the degree of contribution of the two differs for different traits and still needs to be fully understood. Through developmental studies, psychologists and biologists aim to answer these multidisciplinary questions.

Updated on: 13-Apr-2023


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