Question
Hemophilia is a sex‐linked, recessive trait. Which of the following describes the
probability of hemophilia in the offspring of a man who does not have hemophilia
and a woman who is a heterozygous carrier?
A There is a 100% chance that their sons will have hemophilia.
B There is a 0% chance that their daughters will have hemophilia.
C There is a 25% chance that their sons will have hemophilia.
probability of hemophilia in the offspring of a man who does not have hemophilia
and a woman who is a heterozygous carrier?
A There is a 100% chance that their sons will have hemophilia.
B There is a 0% chance that their daughters will have hemophilia.
C There is a 25% chance that their sons will have hemophilia.
Answers
GPT-4o mini
To determine the probability of hemophilia in the offspring of a man who does not have hemophilia (genotype: X^HY, where X^H is the normal X chromosome and Y is the male chromosome) and a woman who is a heterozygous carrier of hemophilia (genotype: X^HX^h, where X^h carries the hemophilia gene), we can analyze the possible combinations of their offspring's genotypes:
1. **For Sons (XY)**
- The mother can pass on either her X^H (normal) or X^h (hemophilia).
- The father can pass on his Y chromosome.
- Possible combinations for sons:
- From the mother: X^H (normal) + Y = X^HY (normal son)
- From the mother: X^h (hemophilia) + Y = X^hY (hemophiliac son)
Therefore, the probability for their sons is:
- 50% chance of being normal (X^HY)
- 50% chance of having hemophilia (X^hY)
2. **For Daughters (XX)**
- The mother can pass on either her X^H (normal) or X^h (hemophilia).
- The father can pass on his X chromosome.
- Possible combinations for daughters:
- From the mother: X^H (normal) + X = X^HX (normal daughter)
- From the mother: X^h (hemophilia) + X = X^hX (carrier daughter)
Therefore, the probability for their daughters is:
- 50% chance of being a normal (X^HX)
- 50% chance of being a carrier (X^hX), but 0% chance of having hemophilia because they will have at least one normal X chromosome.
Based on this analysis:
- **A**: There is a 100% chance that their sons will have hemophilia. **(False)**
- **B**: There is a 0% chance that their daughters will have hemophilia. **(True)**
- **C**: There is a 25% chance that their sons will have hemophilia. **(False, it’s actually 50%)**
Therefore, the correct answer is **B**: There is a 0% chance that their daughters will have hemophilia.
1. **For Sons (XY)**
- The mother can pass on either her X^H (normal) or X^h (hemophilia).
- The father can pass on his Y chromosome.
- Possible combinations for sons:
- From the mother: X^H (normal) + Y = X^HY (normal son)
- From the mother: X^h (hemophilia) + Y = X^hY (hemophiliac son)
Therefore, the probability for their sons is:
- 50% chance of being normal (X^HY)
- 50% chance of having hemophilia (X^hY)
2. **For Daughters (XX)**
- The mother can pass on either her X^H (normal) or X^h (hemophilia).
- The father can pass on his X chromosome.
- Possible combinations for daughters:
- From the mother: X^H (normal) + X = X^HX (normal daughter)
- From the mother: X^h (hemophilia) + X = X^hX (carrier daughter)
Therefore, the probability for their daughters is:
- 50% chance of being a normal (X^HX)
- 50% chance of being a carrier (X^hX), but 0% chance of having hemophilia because they will have at least one normal X chromosome.
Based on this analysis:
- **A**: There is a 100% chance that their sons will have hemophilia. **(False)**
- **B**: There is a 0% chance that their daughters will have hemophilia. **(True)**
- **C**: There is a 25% chance that their sons will have hemophilia. **(False, it’s actually 50%)**
Therefore, the correct answer is **B**: There is a 0% chance that their daughters will have hemophilia.