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.

The best explanation for the difference in skin pigmentation between John and Pat, despite having identical DNA, involves both the polygenic nature of skin color and environmental factors. **Skin color** is indeed a **polygenic trait**, meaning it's influenced by multiple genes. However, **environmental factors** also play a significant role. In this scenario: - **John**, who works in a movie theater, likely has less exposure to sunlight. - **Pat**, as a lifeguard, is frequently exposed to sunlight, leading to increased melanin production and darker skin pigmentation over time. This difference in environmental exposure, particularly to UV radiation from the sun, can cause variations in skin color even among individuals with identical genetic makeup. **Correct Answer:** Skin color, a polygenic trait, is also determined by environmental factors.