Gene Expression and Eye Color

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This Demonstration models the effect of melanin and lipochrome concentration on the color of the human iris. Melanin production is largely influenced by genes, which include the HERC2 and OCA2 genes. HERC2 stimulates the OCA2 gene to induce melanin production. This Demonstration shows how genetic defects in the HERC2 gene can lead to varying amounts of melanin production and, therefore, varying eye color. Use the buttons to set the amount of melanin in the eye, or the HERC2 functionality. Use the slider to control the concentration of lipochrome, which adds or subtracts yellow pigment in the iris.

Contributed by: Jade Babcock-Chi (February 2019)
Open content licensed under CC BY-NC-SA


This was a project for Advanced Topics in Mathematics II, 2018–2019, Torrey Pines High School, San Diego, CA.


[1] A. Jonrik. "Pigment, Lipochrome, Eumelanin and Eye Colour," Your Eye Colour (blog). (Feb 22, 2019)

[2] “Blue and Green Pigments Don't Exist in the Human Iris, So How Do Some People Have Blue and Green Eyes?” Today I Found Out. (Feb 21, 2019)

[3] D. L. Fox, Biochromy: Natural Coloration of Living Things, Berkeley: University of California Press, 1979.

[4] "Genetics of Eye Color." Biotech Basics, Hudson Alpha (Feb 22, 2019) _color.pdf.

[5] L. Southworth, "Eye Color." The Tech Museum of Innovation (Feb 22, 2019)

[6] R. A. Sturm and M. Larsson. "Genetics of Human Iris Colour and Patterns," Pigment Cell & Melanoma Research, 22(5), 2009 pp. 544–562. doi:10.1111/j.1755-148X .2009.00606.x.

[7] D. Zawischa. “Scattering: The Colours of the Sky.” (Feb 21, 2019)


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