John and Pat are identical twins with identical DNA. John works in a movie theater, and Pat works as a lifeguard. They have very different skin pigmentation. Which is the best explanation of the difference? Skin color, a polygenic trait, is also determined by environmental factors. Skin color, a polygenic trait, is also determined by the sex of the individual. Skin color, a trait that demonstrates incomplete dominance, is also determined by environmental factors. Skin color, a trait that demonstrates incomplete dominance, is also determined by the sex of the individual.