Final answer:
The gene-environment interaction for MAOA and conduct symptoms in humans is explained through epigenetic modification, which involves changes in gene expression without altering the DNA sequence. Low MAOA activity due to epigenetic modifications may increase the risk of developing conduct symptoms. The interaction between genetic factors and environmental factors can affect gene expression and behavior.
Step-by-step explanation:
The gene-environment interaction for the example of monoamine oxidase A (MAOA) and conduct symptoms in humans can be explained through epigenetic modification. Epigenetics is the study of how the same genotype can lead to different phenotypes, and it involves changes in gene expression without altering the underlying DNA sequence.
In the case of MAOA and conduct symptoms, epigenetic modifications can influence the expression of the MAOA gene, which is responsible for regulating levels of the neurotransmitter serotonin. An individual with low MAOA activity due to epigenetic modifications may have a higher risk of developing conduct symptoms.
For example, studies have shown that individuals with a specific variation in the MAOA gene combined with a history of childhood abuse are more likely to exhibit aggressive behavior. This demonstrates how the interaction between genetic factors (MAOA genotype) and environmental factors (childhood abuse) can affect gene expression and behavior.