Pretend that eyes only come in three colors, brown, green and blue,

Question

Is it possible for a brown eyed father and a green eyed mother to have a blue eyed child? Explain fully and use a Punnett Square if needed.

Answer 1

yes, they may both have a recessive gene for blue eyes (however it would not show in them because they also have a dominant gene). The child could however, inherit the recessive genes from both parents and in this case would have blue eyes.  

Answer 2

Yes.  There are two primary genes involved in eye color:  B and G.

If you are dominant at the B gene, then you have brown eyes.  So, a person with brown eyes could be:

BBGG

BBGg

BBgg

BbGG

BbGg

Bbgg

If you are homozygous recessive at the B gene, but dominant at the G gene, then you have green eyes.  So, you would have green eyes with the following genotypes:

bbGG

bbGg

To have blue eyes, you must be homozygous recessive at both:  bbgg

So, if a brown eyed person who was BbGg or Bbgg had a child with a green eyed person who was bbGg, the child could be bbgg because both parents can produce gametes that are bg.