Final answer:
It is possible for one identical twin to develop a chronic disease while the other does not due to epigenetics, which involves heritable changes that influence gene expression without changing the DNA sequence itself. These changes can occur due to environmental factors and can lead to different health outcomes in individuals with identical genetic makeups.
Step-by-step explanation:
According to the film "Ghost in Your Genes," it is possible for one identical twin to develop a chronic disease while the other does not due to epigenetics. Identical twins share the same genetic code, but environmental factors can lead to different epigenetic patterns. These patterns can influence gene expression without altering the underlying DNA sequence, leading to variations in the development of diseases such as cancer. Trauma and environmental exposure can result in heritable changes that affect an individual's risk of developing certain conditions. While some diseases can stem from genetic mutations or random chance, the role of the environment is crucial in shaping the epigenome. Environmental triggers in combination with an individual's genetic makeup can determine the likelihood of disease development. Moreover, some heritable mutations, such as those involved in many cancers, don't necessarily need an environmental trigger, while others may increase susceptibility when combined with specific environmental factors.