Editing Eye color (section)

{{short description|Polygenic phenotypic characteristic}}
{{redirect|Iris color|the shade of purple|Iris (color)}}
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{{Use dmy dates|date=December 2021}}
[[File:Farbverlauf Augenfarben.jpg|thumb|upright=1.35|The irises of human eyes exhibit a wide spectrum of colours]]
'''Eye color''' is a [[polygene|polygenic]] [[phenotypic trait]] determined by two factors: the [[pigment]]ation of the [[eye]]'s [[Iris (anatomy)|iris]]<ref name=Wielgus>{{cite journal |vauthors=Wielgus AR, Sarna T|title=Melanin in human irides of different color and age of donors |journal=Pigment Cell Res. |volume=18 |issue=6|pages=454–64 |year=2005 |pmid=16280011 |doi=10.1111/j.1600-0749.2005.00268.x  |issn = 0893-5785}}</ref><ref name=Prota>{{cite journal |vauthors=Prota G, Hu DN, Vincensi MR, McCormick SA, Napolitano A|title=Characterization of melanins in human irides and cultured uveal melanocytes from eyes of different colors |journal=Exp. Eye Res.|volume=67|issue=3 |pages=293–9 |year=1998|pmid=9778410 |doi=10.1006/exer.1998.0518 |doi-access=free }}</ref> and the frequency-dependence of the [[scattering]] of light by the [[Turbidity|turbid]] medium in the [[Stroma of iris|stroma of the iris]].<ref name="Fox1978">{{cite book |last= Fox |first= Denis Llewellyn |title=Biochromy: Natural Coloration of Living Things |publisher= University of California Press |year= 1979 |url=https://books.google.com/books?id=c2xyxwlm2UkC&pg=PA9|isbn= 978-0-520-03699-4}}</ref>{{rp|9}}

In humans, the pigmentation of the [[Iris (anatomy)|iris]] varies from light brown to black, depending on the concentration of [[melanin]] in the [[iris pigment epithelium]] (located on the back of the iris), the melanin content within the iris stroma (located at the front of the iris), and the cellular density of the stroma.<ref name="Wang">{{cite book |doi=10.1109/ICCV.2005.215 |chapter=Separating reflections in human iris images for illumination estimation |title=Tenth IEEE International Conference on Computer Vision (ICCV'05) Volume 1 |year=2005 |last1=Huiqiong Wang |last2=Lin |first2=S. |last3=Xiaopei Liu |last4=Sing Bing Kang|author4-link=Sing Bing Kang |pages=1691–1698 Vol. 2 |isbn=978-0-7695-2334-7 |citeseerx=10.1.1.87.418 |s2cid=2215768 }}</ref> The appearance of blue, green, and hazel eyes results from the [[Tyndall effect|Tyndall scattering]] of light in the stroma, a phenomenon similar to [[Rayleigh scattering]] which accounts for the blue sky.<ref>Sturm R.A. & Larsson M., Genetics of human iris colour and patterns, Pigment Cell Melanoma Res, 22:544-562, 2009.</ref> Neither blue nor green pigments are present in the human iris or [[vitreous humour]].<ref name="Fox1978"/><ref name="Mason">{{cite journal |last=Mason |first=Clyde W. |title=Blue Eyes |journal= Journal of Physical Chemistry | volume=28 |issue=5 |pages=498–501 |year=1924 | doi=10.1021/j150239a007}}</ref> This is an example of [[structural color]], which depends on the lighting conditions, especially for lighter-colored eyes.

The brightly colored eyes of many bird species result from the presence of other pigments, such as [[pteridine]]s, [[purine]]s, and [[carotenoid]]s.<ref name="Oliphant 1">{{cite journal |author=Oliphant LW |title=Pteridines and purines as major pigments of the avian iris |journal=Pigment Cell Res. |volume=1 |issue=2 |pages=129–31 |year=1987 |pmid=3507666 |doi=10.1111/j.1600-0749.1987.tb00401.x }}</ref> Humans and other animals have many [[phenotypic]] variations in eye color.<ref name="Morris">Morris, PJ. [http://www.athro.com/evo/gen/eyecols.html "Phenotypes and Genotypes for human eye colors."] Athro Limited website. Retrieved 10 May 2006.</ref>

The genetics and inheritance of eye color in humans is complicated. {{as of|2010}}, as many as 16 genes have been associated with eye color inheritance. Some of the eye-color genes include ''[[OCA2]]'' and ''[[HERC2]]''.<ref name="Kayser" /><ref name=pmid20944644>{{cite journal |last1=White |first1=Désirée |last2=Rabago-Smith |first2=Montserrat |title=Genotype–phenotype associations and human eye color |journal=Journal of Human Genetics |date=14 October 2010 |volume=56 |issue=1 |pages=5–7 |doi=10.1038/jhg.2010.126 |pmid=20944644 |doi-access=free }}</ref> The earlier belief that blue eye color is a [[recessive trait]] has been shown to be incorrect, and the genetics of eye color are so complex that almost any parent-child combination of eye colors can occur.<ref>[https://www.sciencedaily.com/releases/2007/02/070222180729.htm No Single Gene For Eye Color, Researchers Prove]. Sciencedaily.com (22 February 2007). Retrieved on 2011-12-23.</ref><ref>{{cite web |url=http://www.medterms.com/script/main/art.asp?articlekey=25003 |title=Eye color definition – Medical Dictionary definitions of popular medical terms easily defined on MedTerms |publisher=Medterms.com |date=29 October 2003 |access-date=19 October 2011 |archive-date=5 June 2011 |archive-url=https://web.archive.org/web/20110605231509/http://www.medterms.com/script/main/art.asp?articlekey=25003 |url-status=dead }}</ref><ref name=OCA2>{{cite journal |title=A three-single-nucleotide polymorphism haplotype in intron 1 of OCA2 explains most human eye-color variation |journal=Am. J. Hum. Genet. |volume=80 |issue=2 |pages=241–52 |year=2007|pmid=17236130 |pmc=1785344 |doi=10.1086/510885 |last1=Duffy |first1=David L. |last2=Montgomery |first2=Grant W. |last3=Chen |first3=Wei |last4=Zhao |first4=Zhen Zhen |last5=Le |first5=Lien |last6=James |first6=Michael R. |last7=Hayward |first7=Nicholas K. |last8=Martin |first8=Nicholas G. |last9=Sturm |first9=Richard A. <!--exactly 9 authors--> }}</ref>