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 is a polygenic trait and is also influenced by environmental factors (e.g., sun exposure). Pat’s outdoor work as a lifeguard increases UV-induced melanin production (tanning), explaining the pigmentation difference despite identical DNA.