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.

Answer 1

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

Identical twins can show different pigmentation because environmental exposure (e.g., sunlight/UV for a lifeguard vs. indoor work for a theater employee) alters melanin production and tanning, even with identical DNA.