EVOLUTION OF EYE COLOR ELISE WOOD 11/20/2014

 Ancestry of eye color  What causes different shades to appear  Mutation? Advantage?  Large numbers decreasing to small numbers

Human ancestors- Africa dark pigmentation- eyes, skin and hair were selected for due to hot temperatures/sunlight- darker pigmentation was advantageous Eye color is closely linked with skin color- genes are closely related

HOW IT ALL CHANGED…  Human ancestors began to migrate to various places around world  Selection for darker pigmentation wasn’t as high Mutation arose around Black Sea region OCA2 gene mutation

Blue eyed people came from common ancestor with OCA2 mutation Inherited the same “switch” in the same spot in the DNA Spread of the mutation = advantageous? Theories: Sexual selection- runaway selection like peacocks Sometimes blue eyes is linked with lighter skin

Amounts of melanin Stroma- thick layer of melanin producing cells in iris OCA2 Gene OCA2 gene melanin production in eyes, hair and skin- P protein just affected the iris of the eye Lipochrome HERC2 gene + OCA2 gene Yellow pigmentation + blue = green Yellow + blue + little brown = hazel Rayleigh scattering – blue eyes

GENES TOOK OVER… 16 genes that are associated with eye color Offspring can have any eye color based on genes Alleles from each parent Combinations can be endless

People are able to move all over the world and live in different environments Blue eyed individuals are mating with brown eyed individuals- the recessive blue gene becomes masked Genetics- the blue eyed gene usually loses out to the brown YouTube SciShow Video

Brown eyes are said to be the first eye color that our ancestors had One common ancestor had a mutation in the OCA2 gene- passing it on over generations leading to blue eyes Said to be some advantages to blue eyes, but none have been solidified Mating and genes contribute to the lower levels of lighter eyes Eye color will always vary- gene combinations/alleles/parent copies, etc.