"Human eyes come in a range of colors. Although we typically think only brown, blue, green, and hazel, the eyes can be even more colors, including gray and amber. In very rare cases, eyes can appear red or violet. Individuals with these colors typically produce extremely low amounts of pigment, if any. The red color is from blood.
As with skin and hair, there are the same two-color pigments: eumelanin and pheomelanin. However, there are at least 16 different genes that are known to contribute to eye color.
The color will also appear different depending on whether the pigment is on the front layer of the iris or the back layer of the iris.
Lipochrome is a yellow compound that results from breakdown products from lipids. This molecule contributes to the green and amber eye colors. Light scattering through the layers of the iris leads to the appearance of the blue color as well as green and gray. Individuals with gray eyes have additional collagen fibrils in the iris that make the eye appear gray.
Mutations and polymorphisms in OCA2, a gene involved in melanin production in the eye, have been linked to reduced melanin presence in the front layer of the iris. Such changes result in eye colors other than brown.
Interestingly, individuals with blue eyes do not have mutations in OCA2. Instead, they have a mutation in HERC2, which is adjacent to OCA.
---Scientists believe the evidence suggests that most people with blue eyes all descended from the same individual with a mutation that knocked out Herc2 and OCA2 simultaneously.
----Thus, it is likely that Adam and Eve would have
had brown eyes, as it is clearly a variety of mutations and polymorphisms that contribute to non-brown eye colors due to alterations in the amount of melanin in the outer layer of the iris." AIG
Lipochrome is a yellow compound that results from breakdown products from lipids. This molecule contributes to the green and amber eye colors. Light scattering through the layers of the iris leads to the appearance of the blue color as well as green and gray. Individuals with gray eyes have additional collagen fibrils in the iris that make the eye appear gray.
Mutations and polymorphisms in OCA2, a gene involved in melanin production in the eye, have been linked to reduced melanin presence in the front layer of the iris. Such changes result in eye colors other than brown.
Interestingly, individuals with blue eyes do not have mutations in OCA2. Instead, they have a mutation in HERC2, which is adjacent to OCA.
---Scientists believe the evidence suggests that most people with blue eyes all descended from the same individual with a mutation that knocked out Herc2 and OCA2 simultaneously.
----Thus, it is likely that Adam and Eve would have
had brown eyes, as it is clearly a variety of mutations and polymorphisms that contribute to non-brown eye colors due to alterations in the amount of melanin in the outer layer of the iris." AIG
