Blue-eyed parents can have brown-eyed kids and other eye-oddities ?
Eye color is much more complicated than is usually taught in high school (or presented in The Tech’s eye color calculator). There we learn that two genes influence eye color.
One gene comes in two versions, brown (B) and blue (b). The other gene comes in green (G) and blue (b). All eye color and inheritance was thought to be explained by this simple model. Except of course for the fact that it is obviously incomplete.
New research shows that the first gene is actually two separate genes, OCA2 and HERC2. In other words, there are two ways to end up with blue eyes.
Normally this wouldn’t be enough to explain how blue eyed parents can have a brown eyed child. Because of how eye color works (see below), if one gene can cause brown eyes, it would dominate over another that causes blue. In fact, that is what happens with green eyes in the older model. The brown gene dominates over the green one resulting in brown eyes.
See the video below :
Eye color is a complex trait that depends on the state of several interacting genes. The gene that usually decides the issue (blue eyes or brown eyes) is the OCA2 gene on chromosome 15. But it comes in different strengths. A person with a weak form of the OCA2 gene will have blue eyes. Likewise a person with a strong form will have brown eyes.
The plot thickens, though, because an individual also has other eye-color genes that each has a say in the final eye-color outcome. For example, if one of these lesser genes is strong, it can make the weak form (blue) of OCA2 work much more effectively — almost like the strong form (brown). Then the eye color may be a light brown or muddy grey. In fact, the resulting color can be any shade of brown, hazel/green, or blue depending on the strengths of the interactions.
Source :
How Blue Eyed Parents Can Have Brown Eyed Children
Blue-eyed parents can have brown-eyed kids
Eye color is much more complicated than is usually taught in high school (or presented in The Tech’s eye color calculator). There we learn that two genes influence eye color.One gene comes in two versions, brown (B) and blue (b). The other gene comes in green (G) and blue (b). All eye color and inheritance was thought to be explained by this simple model. Except of course for the fact that it is obviously incomplete.
New research shows that the first gene is actually two separate genes, OCA2 and HERC2. In other words, there are two ways to end up with blue eyes.
Normally this wouldn’t be enough to explain how blue eyed parents can have a brown eyed child. Because of how eye color works (see below), if one gene can cause brown eyes, it would dominate over another that causes blue. In fact, that is what happens with green eyes in the older model. The brown gene dominates over the green one resulting in brown eyes.
See the video below :
Eye color is a complex trait that depends on the state of several interacting genes. The gene that usually decides the issue (blue eyes or brown eyes) is the OCA2 gene on chromosome 15. But it comes in different strengths. A person with a weak form of the OCA2 gene will have blue eyes. Likewise a person with a strong form will have brown eyes.
The plot thickens, though, because an individual also has other eye-color genes that each has a say in the final eye-color outcome. For example, if one of these lesser genes is strong, it can make the weak form (blue) of OCA2 work much more effectively — almost like the strong form (brown). Then the eye color may be a light brown or muddy grey. In fact, the resulting color can be any shade of brown, hazel/green, or blue depending on the strengths of the interactions.
Source :
How Blue Eyed Parents Can Have Brown Eyed Children
Blue-eyed parents can have brown-eyed kids
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