BRAINCAKEHaemophilia
Haemophilia is a sex-linked condition in which the blood does not clot properly. A person with haemophilia bleeds for longer after an injury and may have internal bleeding into joints and muscles, which can cause pain and joint damage.
Blood clotting depends on a cascade of proteins called clotting factors. The genes for two of these are on the X chromosome. Haemophilia A, the most common form, is caused by a faulty allele for factor VIII. Haemophilia B is caused by a faulty allele for factor IX.
Haemophilia is X-linked recessive. Using XH for normal clotting and Xh for haemophilia, affected males are XhY, carrier females are XHXh, and affected females would be XhXh, which is very rare.
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
Key terms in this lesson
- carrier
- A heterozygous individual who carries a recessive allele for a condition without showing it themselves.
More in Genetic Information
- Gene Linkage
- Identifying Linked Genes
- Chromosome Mapping
- Sex-Linkage
- Pedigree Diagrams
- The Albino Trait
- Sex-Linked Diseases
- Red-Green Colour Blindness
All 30 lessons in Genetic Information · All Edexcel A-level Biology topics