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: Gynaecology & Obstetrics
[{'content': 'One of the following is used for sex chromatin testing \nSelect and explain. \nA. Barr body, B. Testosterone receptors, C. Hormone levels, D. Phenotypic features', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Chromosomal sex can be determined by the study of the leucocytes or by simply taking a smear from the buccal mucosa\nThe nuclei of the female chromosome\xa0contain a stainable body called the sex chromatin, hence female cells are termed as chromatin positive.\nIn epithelial cell nuclei, this small peripherally situated darkly staining nodule is called\xa0Barr body\n\nMale cell nuclei lack this body and termed chromatin negative.', 'role': 'assistant'}]