Answer to Question #145482 in Genetics for Vaith

Question

A brown-eyed girl with normal sight got married to a blue-eyed man with normal sight. The father of the girl was blue-eyed and color-blind. What is F1? It is known that gene of brown color of eye dominates over the gene of blue eye color. The gene of color blindness is recessive and X-linked.

Answer 1

Let the gene for color blindness be n, and that for normal color vision be N.

Also let the gene for blue-eyes be b, and that for brown eyes be B.

Then the father of the girl must have been genotype XⁿYbb (blue eyed and color blind)

The genotype of the girl then is XⁿX^NBb and his husband is X^NYbb

There gametes are;

Girl = XⁿB, Xⁿb, X^NB, X^Nb,

Husband = X^Nb and Yb,

                      Girl: XⁿB, Xⁿb X^NB X^Nb

Husband

Yb, XⁿB Yb Xⁿb Yb X^NB Yb X^Nb Yb

X^Nb XⁿB X^Nb Xⁿb X^Nb X^NB X^Nb X^Nb X^Nb

F1 genotypes = Phenotypes

Boys

XⁿB X^Nb = Brown eyes & normal color vision

Xⁿb X^Nb = Blue-eye & normal color vision

X^NB X^Nb = brown eyes & normal color vision

X^Nb X^Nb = Blue eyes & normal color vision

Gils

XⁿB Yb =Brown eyes & color blind

Xⁿb Yb = Blue eyes & color blind

X^NB Yb =Brown eyes & normal color vision

X^Nb Yb = Blue eyed & normal color vision