This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Gene or protein deficient in marfan's syndrome? 
Select and explain. 
A. Fibrillin I, B. Fibrillin II, C. Collagen, D. Elastin
A: Fibrillin I
Answer: A: Fibrillin I 
Explanation: Ans. is 'a' i.e., Fibrillin I Marfan syndrome :? Marfan syndrome results from inherited defect in an extracellular glycoprotein fibrillin -1 on chromosome - 15. It has autosomal dominant inheritance. Pathogenesis Defect in fibrillin affects the elastic recoil of extracellular connective tissue. Elastic fibres consist of a central core made up of elastin, surronded by a peripheral network of microfibrils that consists largely fibrillin. Defect in fibrillin causes defective function of elastic fibres. Microfibrils (containing fibrillin) are mainly distributed to Aoa, ligaments of joint and ciliary zolules of lens - So, in marfan syndrome these tissues are primarily affected.