Final answer:
The refuted argument is that genetics is purely internally determined, as the scenario shows that environmental factors can influence the expression of genetic traits.
Step-by-step explanation:
The argument refuted in the given scenario is genetic information is purely internal influenced. This statement suggests that an individual's genetics is only internally determined and not affected by external factors. However, the scenario demonstrates that despite Lucy possessing a gene for melanoma, by choosing to stay out of the sun she is actively engaging in behavior that can influence the phenotypic expression of her genetic predisposition to the disease. This highlights the fact that environmental factors, such as sun exposure, can impact the way genetic traits are expressed, even when the genetic predisposition exists.