I have brown hair with blond natural blond highlights in it. First off, the hair only turns really blonde when it gets in the sun for a long time. Why do only certain hairs turn blond, and not my whole head?
erm… I want to know the answer too.
Bump
Because traits like hair color are controlled by a huge complex of genes, there’s a huge spectrum of possibilities. This applies not only to different individuals, but to different parts of the scalp on any one individual as well. The gene combinations are the same for different parts of the same scalp, but some of the genes can be inactivated, mutated, or not properly expressed in any given cell. This leads to variations in color of patches of hair (ever seen a dark haired person with a gray patch?) or in individual hairs.
"Melanin is found in two forms. Eumelanin is the dark pigment which predominates in black and brunette hair. Phaeomelanin is a lighter pigment, which is found in red and blond hair. Many people’s hair contains a mixture of the two: the more eumelanin there is in the mixture, the darker is the hair. "