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Naturally occurring red hair appears in a small minority of humans and is the rarest natural hair color, occurring in 0.6 percent of people. [2] A smaller percentage of humans, approximately 0.17 percent or 13 million, have a combination of red hair and blue eyes. [3]
Affected individuals typically have red hair, reddish-brown skin and blue or gray eyes. Variants may include rufous oculocutaneous albinism (ROCA or xanthism). The incidence rate of OCA3 is unknown. [14] [12] OCA4: 606574: SLC45A2: Is very rare outside Japan, where OCA4 accounts for 24% of albinism cases.
Rather, blue eyes result from structural color in combination with certain concentrations of non-blue pigments. The iris pigment epithelium is brownish black due to the presence of melanin. [54] Unlike brown eyes, blue eyes have low concentrations of melanin in the stroma of the iris, which lies in front of the dark epithelium.
Image credits: itsaboatnotaboot Pollen, dust, animal, and certain food allergies (e.g., to nuts, shellfish, and dairy) are fairly common. But their severity has a huge range.
To give a concrete, although imaginary, example in terms of frequencies of characters, consider a case where the “gene for red hair” is closely linked to the “gene for blue eyes”. What does that tell us about the expected population frequency of individuals with red hair and blue eyes?
Melanin in the eyes, in the iris and choroid, helps protect from ultraviolet and high-frequency visible light; people with blue, green, and grey eyes are more at risk of sun-related eye problems. Furthermore, the ocular lens yellows with age, providing added protection.
Red hair, also known as ginger hair, is a human hair color found in 2–6% of people of Northern or Northwestern European ancestry and lesser frequency in other populations. It is most common in individuals homozygous for a recessive allele on chromosome 16 that produces an altered version of the MC1R protein.
"His right eye was light blue, while the left was black, nevertheless his eyes were most attractive", is the description of the historian John Malalas. [ 33 ] [ 34 ] [ 35 ] A more recent example is the German poet, playwright, novelist, scientist, statesman, theatre director, and critic, Johann Wolfgang Goethe .