In class we discussed autosomal polymorphisms such as widow’s peak and detached

Question

ear lobes, both of which are dominant traits. Suppose that a man with a widow’s peak and
attached ear lobes (whose father had detached ear lobes) marries a woman without a widow’s
peak and detached ear lobes (whose father had attached ear lobes). What is the probability
that their first child will:
a. not have a widow’s peak or attached ear lobes?
b. have both a widow’s peak and detached ear lobes?
c. have a widow’s peak and attached ear lobes?

- Does this mean that the womans alleles are wwDd, and the guy's alleles are Wwdd? The guys alleles could be homozygous dominant so WWdd?-

Answer 1

The man has Widow's peak (Ww or WW) and attached earlobes (dd), and the woman without widow's peak (ww) and detached earlobes (Dd, the d is inherited from her father).
So yes,
Man: Wwdd or WWdd (could be either one)
Woman: wwDd.

Case 1: If man has Wwdd (woman has wwDd)
a. no widow's peak NOR attached earlobes
=> wwDd (wwDD is not possible).
P(ww)=1/2
P(Dd=1/2
so P(wwDd)=1/2 * 1/2 = 1/4

b. Widow's peak AND detached ear lobes
=> WwDd (WWDd,WWDD are not possible).
P(Ww)=1/2
P(Dd)=1/2
so P(WwDd)=1/2*1/2=1/4

c. Widow's peak and attached ear lobes
=> Wwdd (WWdd is not possible)
P(Ww)=1/2
P(dd)=1/2
so P(Wwdd)=1/2*1/2=1/4

Case 2: If man has WWdd (woman has wwDd)
a. no widow's peak NOR attached earlobes
=> wwDd (wwDD is not possible).
P(ww)=0
P(Dd)=1/2
so P(wwDd)=0 * 1/2 = 0

b. Widow's peak AND detached ear lobes
=> WwDd (WWDd,WWDD are not possible).
P(Ww)=1
P(Dd)=1/2
so P(WwDd)=1*1/2=1/2

c. Widow's peak and attached ear lobes
=> Wwdd (WWdd is not possible)
P(Ww)=1
P(dd)=1/2
so P(Wwdd)=1*1/2=1/2

Answer 2

Wrong

Answer 3

In humans pattern baldness is a sex-influenced trait, whose degree of expression is controlled by the sex of the individual, such that it is autosomal dominant in males while autosomal recessive in females. On the other hand, colour blindness and haemophilia are both recessive X-linked traits. B = bald; b = non-bald; C = normal vision; c = colour blind; H = normal blood clotting; h = haemophilia. a. Give the genotypes for individuals in the P and F1 generations for the matings below. Assume that no crossing over has occurred. Mating 1 P: bald, non-colour blind, non-haemophiliac female X non-bald, colour blind, haemophiliac male F1: bald, colour blind, haemophiliac male Mating 2 P: bald, colour blind, non-haemophiliac female X bald, non-colour blind, haemophiliac male F1: non-bald, non-colour blind, non-haemophiliac female b. Suppose that the male and female from the F1s marry, what are the probabilities of the male and female offspring outlined below? i. haemophiliac but otherwise normal ii. colour blind and haemophiliac but normal for baldness iii. colour blind but otherwise normal iv. bald, colour