Transcript Evolution of Eye color Elise wood 11/20/2014

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 selectionrunaway selection like
peacocks
Sometimes blue eyes is
linked with lighter skin
•
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
•
Amounts of melanin
•
Yellow + blue + little brown = hazel
•
Stroma- thick layer of melanin
producing cells in iris
•
Rayleigh scattering – blue eyes
•
OCA2 Gene
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
Mating and genes contribute
to the lower levels of lighter
eyes
One common ancestor had a
mutation in the OCA2 genepassing it on over generations
leading to blue eyes
Said to be some advantages to
blue eyes, but none have been
solidified
Eye color will always vary- gene
combinations/alleles/parent
copies, etc.
http://evolution.about.com/od/humans/a/Evolution-Of-Eye-Color.htm
http://www.sciencedaily.com/releases/2008/01/080130170343.htm
http://genetics.thetech.org/ask-a-geneticist/origin-blue-eyes