Many family members, and some friends, have marvelled at the fact that Fletch has blue eyes. How can this be? I mean, Rick and Jen both have brown eyes. Fear not, my confused friends, I am here to help explain.
Let's let "B" (capital B) represent a gene for brown eyes, and "b" (lower case) for blue eyes. Eye color is the result of 2 genes, 1 from Mom and 1 from Dad. So, a child will have a 2-gene combination, one of the following: BB, Bb, or bb. Have your eyes glazed over yet? (There is no gene for glazing over.)
Brown is a dominant gene. If B is present, the child will always have brown eyes.
My Dad has blue eyes, and my Mom had brown. Since a brown gene, if present, will always present brown eyes, then it stands to reason that my Dad's gene sequence for eye color is "bb" (2 blue genes). My Dad could ONLY pass on a blue gene "b" to me, so we know that I have at least ONE "b" gene (blue). But I have brown eyes, therefore I also have a "B" gene, which I must have received from Mom. So, my personal gene sequence for eye color is "Bb". A similar story exists for Jen, whose mother had green eyes (blue, from a genetic standpoint).
Rick: Bb
Jen: Bb
So, if you got into some boring combinational mapping, you would see that there is exactly a 25% chance that any one of our children will have blue eyes. Fletch has blue eyes ("bb"): I gave him one "b" and Jen gave him the other "b."
Fletcher beat the odds.
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2 comments:
Call me dumb, but how do green and blue differ? Why couldn't Fletcher have had green eyes?
How does a baby get green eyes??
F-I-L
My limited understanding is that green and blue eyes have the same gene, just different amounts of pigment which makes them different color. I could be wrong on that.
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