Q. Christmas factor is involved in ____:
Answer: Blood Coagulation
Notes: Factor IX, also known as Christmas factor, is one of the serine proteases of the coagulation system; it belongs to peptidase family S1. Deficiency of this protein causes Haemophilia B. It was discovered in 1952 after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to haemophilia.