Respuesta :
John and Pat's occupation best explains the difference between their skin pigmentation. Since Pat works as a lifeguard, she is more exposed to the sun, which tans her skin. John, on the other hand, works in the theater, where he isn't exposed to sunlight that much, so he is much lighter than his twin, Pat.
And melanin is produced by the body. The amount created is not entirely genetic, but instead dependent on the amount of sunlight received