National Geographic : 2017 Jun
the perils of pale 79 Epidermis surface skin layer ENLARGED BELOW Dermis lower skin layer hair Pheomelanin Melanosome Melanocyte Eumelanin Typical melanosome Melanosome with albinism NORMAL SKIN SKIN WITH ALBINISM Melanin absorbs sunlight Sunlight passes through unobstructed lighter Range of skin tones darker PEOPLE WORLDWIDE 1 in 40,000 Frequency of OCA-2 Albinism AFRICAN AMERICANS 1 in 10,000 TANZANIANS 1 in 1,400 GUNA PEOPLE (PANAMA) 1in70 Shielding skin from the sun Melanin is the main pigment in the skin of humans and all other mammals. When sunlight hits the skin, mela- nin covers the nuclei of skin cells and absorbs damaging ultraviolet rays. PROTECTIVE PIGMENT Cells with branching arms called melanocytes create melanin in melanosomes, vesicles that flow into the surrounding cells to protect them. RANGE OF COLOR Human skin has two types of melanin: brownish black eumelanin and reddish yellow pheomelanin. The mixture of these two variants determines skin color. ALBINISM’S PIGMENT PROBLEM Although melanocytes in skin with albinism produce melano- somes, those melanosomes either completely lack melanin or have significantly less than usual.