This also explains why two brown-haired parents can produce a blonde-haired child. A person with a brown allele will have brown hair a person with no brown alleles will be blonde. One gene, which is a brown/blonde pair, has a dominant brown allele and a recessive blonde allele. According to one theory, at least two gene pairs control human hair color. The genetics of hair colors are not yet firmly established. As the phaeomelanin continues to break down, the hair will gradually become orange, later yellow, and then white. This is the reason bleach will cause darker hair to turn reddish-brown during the artificial coloring process. Phaeomelanin is more chemically stable than black eumelanin, but less chemically stable than brown eumelanin, so it breaks down more slowly when oxidized. Although most noticeable in red-heads, all humans have varying concentrations of phaeomelanin in their hair. High amounts of black eumelanin results in black hair, while low concentrations of black eumelanin in the hair results in gray hair color. A low concentration of brown eumelanin in the hair results in blonde hair, whereas a higher concentration of brown eumelanin will color the hair brown. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color. There are two types of pigments that give hair its color: eumelanin and phaeomelanin.
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