how are freckles formed? And why do they seem more common in redheads?
In: Biology
freckles are a form of irregular tanning in which the melanin that is normally produced by a suntan is concentrated in clusters of UV-sensitive melanin producing cells (melanocytes) instead of evenly darkening the skin like in other skin types which have a more even distribution of melanocytes.
They’re common in redheads because of their prevalence in northern Europeans who have the MC1R gene.
Freckles form as a result of sun exposure. UV light triggers melanocytes in the skin to produce melanin in response to UV damage as a protective measure. For people who form freckles it is because the melanocytes in certain areas produce significantly more melanin than the surrounding melanocytes, causing an uneven distribution. Redheads have the MC1R gene which dramatically increases the likely hood of overactive melanocytes. The MC1R gene loads the gun while UV exposure pulls the trigger for freckle formation. A baby who has never been exposed to the sun does not have any freckles as a result. Because the sun in Northern Europe is not nearly as strong as it is elsewhere, there isn’t much of an evolutionary pressure for melanin to be evenly deposited to form a strong protective layer.
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