Anatomy and Physiology for Multiple Organ Systems Practice Test

Gene-environment interaction describes how the same genetic makeup can lead to different phenotypes depending on environmental conditions. In genetically identical individuals, differences in environment can change how genes are expressed through regulatory processes and epigenetic modifications, such as DNA methylation or histone changes, without altering the DNA sequence itself. This means one twin might develop a trait or disease risk that the other does not, because their bodies are turning genes on or off differently in response to nutrition, stress, toxins, or lifestyle. The environment does not change the genotype, and gene expression is not fixed regardless of environment, so those other statements aren’t accurate.