Haemophilia A is caused by the deficiency of
Correct answer: A. clotting factor VIII
- A. clotting factor VIII
- B. vitamin K
- C. platelets
- D. haemoglobin
Explanation
The X linked recessive gene codes for antihaemophilic factor VIII, and without it the clotting cascade stalls, so even a small injury bleeds for a very long time and bleeding into joints is common. Vitamin K deficiency also impairs clotting but does so by affecting several liver made factors and is dietary rather than inherited. The platelet count in haemophilia is normal.
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About X-linked Recessive Inheritance
X-linked recessive inheritance involves genes on the X chromosome, so males express a recessive allele with no corresponding allele on their single X chromosome, while females may be carriers. Pedigrees cover haemophilia and red-green colour blindness, including carrier mothers, affected sons and the absence of father-to-son transmission.
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