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: Biochemistry
[{'content': 'Phenylketonuria is detected by which urine test: \nSelect and explain. \nA. Guthrie test, B. Sodium nitroprusside test, C. Blot test, D. FeCl3', 'role': 'user'}, {'content': "Answer: A \nExplanation: Guthrie Test: It is a rapid screening test. Ceain strains of bacillus subtilis need phenylalanine as an essential growth factor. Bacteria cannot grow in a medium devoid of phenylalanine. Bacterial growth is propoional to the phenylalanine content in the patient's blood. Good to know: Ferric chloride Test: Phenyl ketones in urine can be detected by this test. A transient blue-green color is a positive test. Nitroprusside Test is used for the colour reaction of amino acid Sulfhydryl group (Cysteine.) Ref: Textbook of Biochemistry DM Vasudevan, 5th Ed Page 22, 206", 'role': 'assistant'}]