How do two brown-eyed parents have a blue-eyed child?

Question

My husband has blue eyes; both his parents (yes they are his real parents) have brown eyes. How does this happen? At school, I was always told that brown eyes are the dominant eye colour.

Answer 1

It is because brown eyes are dominant that they can hide for generations. Here's a quick explanation.

You inherit two genes for each trait, one from each parent. But in order for you to have brown eyes, you only have to inherit a brown gene from one parent. The other gene can be blue - but it will be overridden by the brown gene. If you then have children with a person who also has one brown gene and one blue gene, the child has a 25% chance of inheriting two blue genes and will therefore have blue eyes.

If B represents a Brown gene, and b represents a blue gene, the family tree looks like this:

Mother - Bb - brown eyes
Father - bB - brown eyes

Child can be any one of these:
Bb - brown eyes
BB - brown eyes
bB - brown eyes
bb - blue eyes

Answer 2

all I know is that the brown eye gene is dominant over blue, you really have to look back on the history also. Seeing that it's two brown-eyed people, then the only chance of getting a blue eyed child would be very little, I'm just not sure where green eyes would fit in. I have no yet about other gene colors of eyes accept for Brown and Blue

Answer 3

This Site Might Help You.

RE:
How do two brown-eyed parents have a blue-eyed child?
My husband has blue eyes; both his parents (yes they are his real parents) have brown eyes. How does this happen? At school, I was always told that brown eyes are the dominant eye colour.

Answer 4

brown gene is dominant so two brown eyed people could give
2 pure blue genes , 2 pure brown genes or 1 blue and 1 brown gene
all but the 2 blue combination should give brown eyes
you will probably have a grandparent with blue eyes
two blue eyed parents should have blue eyed children it should be impossible to have brown eyed children from two blue eyed parents

Answer 5

it works like this

if big B is the gene for brown eyes, and little b is the gene for blue eyes, OK?

but eye colour is decided by more than one gene, and the gene for brown eyes is dominant, which means that it is the deciding factor if both genes are present.

so if a person has BB they will have brown eyes
if the have Bb or bB they will have brown eyes
if they have bb they will have blue eyes.

and if two parents both have Bb, their genes could possibly join together in one of four ways:

BB
Bb
bB
bb

the first three combinations would result in a brown eyed child, the last one a blue eyed child.

Answer 6

Recessive genes, nondominant blue gene carried by both parents (brown obviously dominant here) passed down to child so they have two of the blue eyed gene because there is no dominant gene, they have blue eyes.

Answer 7

Basic genetics. Yes, brown is supposed to be the dominant colour, but in some people the genes are stronger with a different colour. Not everything can be explained away by science and they do get it wrong. Both my parents have blue eyes, but my sister and I have green eyes inherited from our grandmother. It's the uniqueness and complexity of a situation like this that gets us questioning science!

Answer 8

Brown colour is dominant so his both parents must have the blue eyes as recessive gene. It's a 25% chance for the blue eyes to occur.

Answer 9

If his parents both have a recessive gene for blue eyes there's a one in four chance they could 'outmatch' the dominant brown eye gene and produce a child with blue eyes like your husband.

Answer 10

This was actually asked in my biology class...I actually have two blue eyed kids and I have hazel eyes and their father have brown eyes. What happened was his parents werent homozygous they were heterozygous so the had a recessive gene that allowed your husband to have blue eyes.