Question

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.

Explanation:

Skin color is a polygenic trait (influenced by multiple genes). John (movie - theater worker) and Pat (lifeguard) have different sun - exposure (environmental factor). Sun exposure affects melanin production (skin pigmentation). So, the difference in their skin pigmentation is due to skin color being a polygenic trait also influenced by environmental factors. The sex of the individual is not relevant here as they are twins (same sex assumed, since no info to suggest otherwise). Skin color is not an incomplete - dominance trait.

Answer:

Skin color, a polygenic trait, is also determined by environmental factors.