This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Osteology, Subject name: Pathology
In osteogenesis imperfecta the defect is in the: 
Select and explain. 
A. Synthesis of type I collagen, B. Mineralisation of osteoid, C. Osteoclast function, D. Osteoblast formation
A: Synthesis of type I collagen
Answer: A: Synthesis of type I collagen 
Explanation: Ans; a (Synthesis of type I collagen) Ref: Robbins, ed, p. 1279Osteogenesis imperfecta is due to deficiency in the synthesis of Type I collagen structures affected are - bone, joints,eyes, ear, skin and teethCytogenetic abnormality:Mutation in the genes that codes for a1, and a2 chains of collagen autosomal dominant inheritanceClinical features:All types are characterized by extreme skeletal fragilityOther features are blue sclera, hearing impairment,Dentiogenesis imperfecta, growth retardation etcREMEMBER:Type of osteogenesis imperfecta incompatable with life = type IIType of osteogenesis imperfecta with normal sclera = type IVBRIDGE:Van der hoeve's syndrome - AD osteogenesis imperfecta, blue sclera, hearing loss