Question
A prospective mother decided to undergo genetic testing, and she found out that she is a carrier for hemophilia. Her husband passed all of his tests and confirmed that he does not have hemophilia.
If the parents have a son, what chromosome will the father have passed on?
The couple finds out they’re having a boy. What are the chances he will have hemophilia? %
The couple finds out they’re having a girl. What are the chances she will have hemophilia?
If the parents have a son, what chromosome will the father have passed on?
The couple finds out they’re having a boy. What are the chances he will have hemophilia? %
The couple finds out they’re having a girl. What are the chances she will have hemophilia?
Answers
GPT-4o mini
Hemophilia is typically an X-linked recessive disorder. This means that the gene causing hemophilia is located on the X chromosome. In terms of inheritance:
1. **Parental Genotypes:**
- The mother is a carrier for hemophilia, so her genotype is X^h X (where X^h is the X chromosome carrying the hemophilia allele and X is the normal X chromosome).
- The father does not have hemophilia, so his genotype is X Y (normal X chromosome and a Y chromosome).
2. **If the parents have a son:**
- The father contributes his Y chromosome to the son (since sons inherit the Y chromosome from their fathers).
- The mother can contribute either of her X chromosomes (X^h or X).
This results in:
- If the mother passes on X^h: The son’s genotype will be X^h Y (meaning he will have hemophilia).
- If the mother passes on X: The son’s genotype will be X Y (meaning he will not have hemophilia).
**Chances for the son having hemophilia:**
- There is a 50% chance the son will inherit the X^h from his mother, thus he has a **50% chance of having hemophilia**.
3. **If the parents have a girl:**
- The father contributes his X chromosome to the daughter.
- The mother can contribute either of her X chromosomes (X^h or X).
This results in:
- If the mother passes on X^h: The daughter’s genotype will be X^h X (meaning she will be a carrier of hemophilia but not necessarily express the condition).
- If the mother passes on X: The daughter’s genotype will be X X (meaning she will not be a carrier and will not have hemophilia).
**Chances for the daughter having hemophilia:**
- The daughter will either be X^h X (carrier) or X X (normal), but she would need both X chromosomes to carry the hemophilia allele to have hemophilia.
- Since the father provides one normal X chromosome, it is not possible for the daughter to be affected by hemophilia.
- Thus, the chances of the daughter having hemophilia is **0%**.
In summary:
- **Chance for the son to have hemophilia:** 50%
- **Chance for the daughter to have hemophilia:** 0%
1. **Parental Genotypes:**
- The mother is a carrier for hemophilia, so her genotype is X^h X (where X^h is the X chromosome carrying the hemophilia allele and X is the normal X chromosome).
- The father does not have hemophilia, so his genotype is X Y (normal X chromosome and a Y chromosome).
2. **If the parents have a son:**
- The father contributes his Y chromosome to the son (since sons inherit the Y chromosome from their fathers).
- The mother can contribute either of her X chromosomes (X^h or X).
This results in:
- If the mother passes on X^h: The son’s genotype will be X^h Y (meaning he will have hemophilia).
- If the mother passes on X: The son’s genotype will be X Y (meaning he will not have hemophilia).
**Chances for the son having hemophilia:**
- There is a 50% chance the son will inherit the X^h from his mother, thus he has a **50% chance of having hemophilia**.
3. **If the parents have a girl:**
- The father contributes his X chromosome to the daughter.
- The mother can contribute either of her X chromosomes (X^h or X).
This results in:
- If the mother passes on X^h: The daughter’s genotype will be X^h X (meaning she will be a carrier of hemophilia but not necessarily express the condition).
- If the mother passes on X: The daughter’s genotype will be X X (meaning she will not be a carrier and will not have hemophilia).
**Chances for the daughter having hemophilia:**
- The daughter will either be X^h X (carrier) or X X (normal), but she would need both X chromosomes to carry the hemophilia allele to have hemophilia.
- Since the father provides one normal X chromosome, it is not possible for the daughter to be affected by hemophilia.
- Thus, the chances of the daughter having hemophilia is **0%**.
In summary:
- **Chance for the son to have hemophilia:** 50%
- **Chance for the daughter to have hemophilia:** 0%