Question

In humans, blue eyes are caused by a recessive allele ("b") that dilutes pigment production. BB and Bb individuals have brown eyes and bb individuals have blue eyes. Red-green color blindness is caused by the X-linked recessive allele Xc. The 2 loci assort independently. If a BbXcX mother and a BbXY father have a son, what is the probability that the son will be: color-blind?_________________________blue-eyed? __________________________blue-eyed and color-blind? ___________________

Answer 1

Answer:

Probability that the son will be:

color-blind = 1/2

blue eyed = 1/8

blue eyed and color-blind = 1/16

Explanation:

Mother : BbXcX

Father : BbXY

Colorblindness is X linked recessive trait hence will be caused when the son has XcY genotype.

XcX   X    XY :

     Xc    X

X  XcX  XX

Y   XcY  XY

Half of the sons will have normal vision and other half will be colorblind hence, there is 1/2 probability that the son will be colorblind.

Eye color is autosomal trait and blue color will be produced when the child has bb genotype.

Bb     X    Bb  :

   B    b

B  BB  Bb

b  Bb   bb

1/4 of the children will have blue eyes. Since half of the children are expected to be males, 1/4 * 1/2 = 1/8 sons are expected to have blue eyes.

Probability of a son being blue eyed and color blind will be :

1/8 * 1/2 = 1/16