IB Biology SL D3.2.12 Haemophilia Questions
Use X-linked allele notation, pedigrees and Punnett grids to explain haemophilia inheritance and sex-specific risk in IB Biology SL D3.2.12.
- Syllabus
- First assessment 2025
- Course
- Biology SL
- Level
- SL
Exam points
- Represent haemophilia as an X-linked recessive disorder, using X-linked allele notation to identify carrier females and affected males.
- Use an X-linked Punnett grid or pedigree evidence to calculate haemophilia genotypes, phenotypes and sex-specific probabilities.
Learn this topic
IB Biology SL D3.2.12 Haemophilia Questions question 1
[Maximum number: 3]
People with the inherited disease hemophilia have a deficiency in one of the proteins that act as clotting factors in blood.
A family has a history of hemophilia that is caused by a sex-linked recessive allele. A woman from this family is a carrier and marries a man who does not have the allele. Showing your working, determine the probability of their children having the disease.
Alleles clearly labelled for both parents, in a Punnett square or other format.
Correct genotypes for all four possibilities for children.
| Father: \(X^{H}\) | Father: \(Y\) | |
|---|---|---|
| Mother: \(X^{h}\) | \(X^{H}X^{h}\) | \(X^{h}Y\) |
| Mother: \(X^{H}\) | \(X^{H}X^{H}\) | \(X^{H}Y\) |
Phenotypes of the children:
The sons would have a 50% chance of having hemophilia.
The daughters would have a 0% chance of having hemophilia / 50% chance of being a carrier.
All question bank results loaded