Final answer:
Environmental factors can influence genetic traits by determining if a genetic trait becomes a health issue and by affecting the expression of genes in an organism's phenotype.
Step-by-step explanation:
Environmental factors can influence genetic traits in several ways. They can determine if a genetic trait becomes a health issue, as seen in the case of people with a genetic predisposition to certain diseases who may or may not develop those diseases depending on their environment. Additionally, environmental factors can affect how genes are expressed in an organism's phenotype. For example, sunlight and food availability can impact the expression of genes related to skin color and body size.