Question

A woman with genotype Dd Aa Bb has a child with a man who is dd Aa Bb.

DD and Dd are for thick lips, dd is for thin lips.

AA, Aa are brown eyes and aa are blue.

BB and Bb are thick brows and bb is thin brows.

a) What is the probability that their child will have thin lips, brown eyes and thick eyebrows.

b) What is the probability that their child will have either brown eyes or thin eyebrows.

C) the man also happens to be red-green color blind (x-linked recessive). The woman is not color blind but her father was. If their future child were a daughter wha us the probability that the male would display/carry the color-blind trait if their daughter has children with an unaffected male? What about the female?

Answer 1

a)  Dd Aa Bb X dd Aa Bb Parental cross

Probability for the child to have thin lips is ,

	D	d
d	Dd	dd
d	Dd	dd

Thus the probability is 2/4=1/2

Similarly we can calculate the probability for brown eyes and thick eyebrows as 3/4 and 3/4 respectively.

therefore, the probability that their child will have thin lips, brown eyes and thick eyebrows= 1/2 X 3/4 X 3/4

= 9/32

b.) The probability that their child will have either brown eyes or thin eyebrows can be determined by addition rule of probability. The probability for brown eyes and thick eyebrows are 3/4 and 3/4 respectively.

Therefore, The probability that their child will have either brown eyes or thin eyebrows = 3/4+3/4= 3/2

c.) Since the woman is not colour blind but her father is, the genotype of the woman will be XX^c. The man is colourblind and hence his genotype is X^cY.

	Xc	Y
X	XcX	XY
Xc	XcXc	XcY

The probability of daughter being affected is 1/2.

If this daughter has children with an unaffected male then the son that she has would be 100% affected while daughters would be carriers.

P.S.: The second part of question C is not very clear. I have still answered the question from whatever I could understand. Kindly check the question again.