What Does Your Eye Color Say about You?

What Does Your Lye Color Say About You? They say the eyes are the window to the soul, but they are also a uindour to your genes. Your iris, the pigmented part of your eye, regulates how much light enters your eye, but it also protects internal organs from harmful UV-radiation. But why are irises colored at all? How Eye Color Develops from ? Birth to Adulthood Muscle Fibers How can a baby be born with blue eyes, but have brown eyes as an adult? Melanocytes The Cause: Quantity of a protein pigment known as melanin in the iris cells, known as stroma. •A lot of melanin in the stroma gives a person dark brown . Much less melanin equals blue eyes. eyes. • Within 6 and 36 months, her special melanocyte stroma cells will start to produce melanin. When a baby is born, he will have almost no melanin in his stroma, giving his blue eyes. • Melanin concentration determines her final eye color. Some babies of African or Asian decent are born with blue eyes. But, more often they are born with brown eyes because of a high concentration of melanin at birth. ? 2 Genetics behind Eye Color But what determines how much It's all in the genes melanin concentration in your irises? There is no single gene that determines what color your eyes will be. Historically, brown eyes were thought to be dominant over blue eyes. However, modern science has proved that eye color is a multi-gene trait, not a single gene trait. These genes control the amount of melanin inside the iris. old Science: Single Gene Trait Ileur Science: Many Genes Contribute to Eye Color I Two genes are mainly responsible | for eye color: OCA2 & HERC2. | • OCA2 controls nearly 3/4 of the blue-brown color spectrum. Brown eye Father Blue eye Mother • HERC2 influences the expression of the OCA2 gene. Blue eye C hild OCA2 = Brown (B) & Blue (b) variations gene gey gene = green (G) & Blue/hazel (b) variations Wheel of Eye Color Fortune IERC2 Gey Eye Color GG Gb BB Brown • Brown version of HERC2 is B; blue version is b. Green version of gey is G blue version is b. BB Brown BB bb Brown Bb GG Brown Bb Gb Brown There are two copies of each eye color gene from each parent. • This chart depicts all of the unique combinations and which eye color they would produce in an offspring. Bb bb Brown bb GG Green bb Gb Green bb bb Blue Your Eye Depends on Gene Combination HERC2 HERC2 HERC2 gey or gey gey gey Brown version of HERC2 = brown eyes regardless of the gey gene. Blue versions of HERC2 = version of gey gene determines your eye color. • If HERC2 is blue and gey is green, you have green Blue versions of both genes = blue eyes. eyes. All Eye Colors: Most Common And Rarest Eye Colors Scientists now know that there is more to eye color than the simple colors like blue, green, and brown. • Eye color exists along a continuum from the lightest blue to the darkest brown and everything in between. LYST gene DSCR9 gene 17q25.3 Three new genes that contribute to subtle eye color variations: Your eye COLÓR The greatest variation in eye color is seen in people of European descent. • OCA2 • DSCR9 gene • gey • Most common eye color: Brown. • HERC2 •17q25.3 • Second most common color: Blue or grey. •LYST gene Common in Northern Europe where UV-radiation is less. • Rarest eye color: Green This is a result of several other genes scientists are just now mapping: HERC2 qene X) Can shut off the OCA2 gene, which will give a person blue eyes. • All blue-eyed people • This means all blue-eyed people came from the same have this DNA difference. ancestor! First blue-eyed human EVER! Rarer still are eye color ANÖNALIES: ALbinos Heterochromia • They have almost no melanin, so their irises are clear but appear pink or red because we can see their blood vessels. • means your genes have given you two different colored irises, • or that one iris has two distinct colors. Eye Colors Changing Over time Did you know that your eye color can change over time? • Eyes do not continuously produce pigment like hair or skin, but > Jour iris can lighten > Jour iris can darken • if the number of pigment granules in • if the number of pigment granules your stroma decrease, in your stroma increases. • or the pigment • or stroma starts producing lighter pigments. degrades, Why? Again, your genes are to blame. Eye color also changes over generations. • For instance, blue eyes are becoming increasingly rare in American children in the last few decades Scientists are InCOvering neus information about human eye color every year, but that doesn't change the fact that the piqment of our eges says a lot about uho uwe are. What does your eye color tell people about you? XXXXX Sources http://www.thetech.org/genetics/ask.php?id-316 http://www.sciencedaily.com/releases/2007/02/070222180729.htm http://www.sciencedaily.com/releases/2008/01/080130170343.htm http://www.sciencedaily.com/releases/2010/05/100506172731.htm http://www.thetech.org/genetics/news.php?id%3D76 http://www.thetech.org/genetics/news.php?id%3D39 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2865509/ http://www.usatoday.com/tech/columnist/aprilholladay/2004-10- 08-wonderquest x.htm