I know that a blue eyed couple can't produce a brown eyed baby so?

Question

why can a brown eyed couple produce a blue/green eyed baby?

Answer 1

To simplify, in order for a person to have blue eyes they must inherit the blue-eye gene from both parents - one from each. However, a brown-eyed person can have one blue-eye gene and one brown-eye gene - this is because the brown-eye gene is dominant, so always masks the effect of the blue-eye gene.

So two parents with brown eyes could each have one brown-eye and one blue-eye gene. Which gene is passed on from each parent to the child is more or less random, so on average one out of four of their children would inherit blue-eye genes from both sides.

If B is the gene from brown eyes, and b the gene for blue eyes, four children would come out like this:
B/B - brown eyes
B/b - brown eyes
b/B - brown eyes
b/b - blue eyes

Hope that makes sense. It should also be clear that if both parents have blue eyes, they must necessarily have two blue-eye genes each, so therefore couldn't pass on a brown-eye gene to a child.

Answer 2

Here is an analogy, Each parent has one dollar. Blue eyed parents have 4 quarters so if they are going to make a dollar for their child it can only be made up of 4 quarters.

A brown eyed couple each has one quarter and one 50 cent piece so they can make their child a dollar using either 2 50 cent peices, 1 fifty cent and 2 quarters or using all 4 quarters. If they give the child the 4 quarters than the kid has the same breakdown as our original blue-eyed couple (so he has blue eyes).

Now there are some brown eyes who only have 2 fifty cent pieces so they cannot ever give a child 4 quarters.

Hope that made some sense!

Answer 3

The gene for blue eyes is a recessive trait so if the parents are both blue eyed they are homozygous with the recessive genes and therefore can only produce a blue eyed baby.

If someone has brown eyes they may be heterozygous, possessing the recessive trait, so if both parents are brown eyed and both posses the recessive blue eye trait there is a 1 in 4 chance of producing a blue eyed child.

Answer 4

I don't know the recessive/dominant order if this is a one-gene trait or even if it is a one-gene trait. Since the eye coloring is what is called "hazel", there may well be a genetic make-up to produce that coloring from a brown-eyed couple

Answer 5

blue eyes requires both genes for eye colour to be recessive
brown eyes might have one gene that is n't brown
it might be blue or green
so the chances of the baby having two recessive genes to make a blue eyed baby or a green eyed baby is possible.

Answer 6

the blue colour of the eye is a reccessive trait, therefore it needs two reccessive alleles to show as a characteristic. the brown eyed parents must be heterozygous for the trait, mean they both carry 1 reccessive allele for blue eyes and one dominant allele for brown eyes

Answer 7

The couple can't have a baby with that colour eyes because it is not in their genes to pass to the child.

Answer 8

Both heterozygous and the baby inherited the recessive from both.

Answer 9

Look up mendelian genetics