In class we discussed autosomal polymorphisms such as widow’s peak and detached
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?-
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
Wrong
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
To determine the probability of the traits in the offspring, we need to analyze the genotypes of the parents. Let's assign symbols to represent the widow's peak (W) and detached ear lobes (D) as dominant traits, and lowercase letters (w, d) for the corresponding recessive alleles.
Assuming the man has a widow's peak and attached ear lobes, we can represent his genotype as follows: WwDd. This means he carries one dominant allele (W) for widow's peak and one recessive allele (w) for detached ear lobes. Similarly, he carries one dominant allele (D) for attached ear lobes and one recessive allele (d) for detached ear lobes.
Now, let's consider the woman who does not have a widow's peak and detached ear lobes. If her father had attached ear lobes, we can deduce that her genotype is wwdd, as she does not have the dominant alleles for either trait.
Taking these genotypes into account, let's determine the probability of each outcome for their first child:
a. To calculate the probability that the child does not have a widow's peak or attached ear lobes, we need to find the chances of the child inheriting the recessive alleles from both parents, which are w and d. Since both parents have at least one recessive allele for each trait, the probability is 1/4 or 25% (WW, WD, DW, and DD are all possibilities, and only wwdd does not have the traits).
b. To determine the probability of the child having both a widow's peak and detached ear lobes, we need to consider the chances of inheriting the dominant alleles from both parents. Since the father has one dominant allele for each trait (W and D) and the mother has none, the probability is 0% (there is no way for the child to inherit both dominant alleles).
c. Lastly, the probability of the child having a widow's peak and attached ear lobes can be calculated by considering the chances of inheriting the dominant allele for the widow's peak (W) from the father and the attached ear lobes (D) from both parents. Since the father has a dominant allele (W) for the widow's peak and a recessive allele (d) for detached ear lobes, and the mother has recessive alleles (w and d) for both traits, the probability is 1/4 or 25% (WD, DW, and DD are possibilities, while WW is not possible).
In summary:
a. Probability of not having a widow's peak or attached ear lobes: 25%
b. Probability of having both a widow's peak and detached ear lobes: 0%
c. Probability of having a widow's peak and attached ear lobes: 25%