This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood disorder, Subject name: Pathology
Most common mutation in haemophilia is: 
Select and explain. 
A. Intron 1 inversion, B. Intron 22, C. 619 bp deletion, D. 3.7 bp deletion
B: Intron 22
Answer: B: Intron 22 
Explanation: Genetic abnormalities in haemophilia : Inversions: Intron 22 inversion, Intron 1 inversion Point mutations: Missense mutation, nonsense mutation, frameshift mutation Deletion of pa or whole of gene Inseion of repetitive sequences Splicing errors affecting production of mRNA Hemophilia A(factor 8 deficiency) -x linked recessive trait, affects mainly males and homozygous females Hemophilia B - x linked disorder caused by mutations in coagulation Factor 9