Question

If a brown-eyed man marries a blue-eyed woman and they have ten children, all brown-eyed, can you be certain that the man is homozygous? If the eleventh child has blue eyes, what will that show you about the father’s genotype?

Answer 1

It is very likely, but not certain. If the eleventh child has blue eyes, barring adultery, he must be heterozygous.

Answer 2

it is possible that he would be homozygous but not ccertain because some males have an extra chromosome foe example : the normal male has "XY" and another male may have "XXY" which means its possible for a male to be heterozygous but its not common.
Now if the eleventh child has blue eyes then that shows that the man's genotype is homozygous for brown-eyes , when u work out the cross these are the phenotypes "XB Xb, XB Xb, Xb Y, Xb Y" so the chances that the child has blue eyes or brown eyes are 50/50 ( Let 'b' represent blue eyes, recessive and Let 'B' represent brown eyes,dominant