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
One of the following is used for sex chromatin testing 
Select and explain. 
A. Barr body, B. Testosterone receptors, C. Hormone levels, D. Phenotypic features
A: Barr body
Answer: A: Barr body 
Explanation: Chromosomal sex can be determined by the study of the leucocytes or by simply taking a smear from the buccal mucosa
The nuclei of the female chromosome contain a stainable body called the sex chromatin, hence female cells are termed as chromatin positive.
In epithelial cell nuclei, this small peripherally situated darkly staining nodule is called Barr body

Male cell nuclei lack this body and termed chromatin negative.