This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Which of the following would form the basis for karyotyping studies in female? 
Select and explain. 
A. Phenotype abnormality, B. Testoterone quantity, C. Barr body, D. Not recalled
C: Barr body
Answer: C: Barr body 
Explanation: Females contains two 'X'chromosomes. An extra 'X' chromosome contains Barrbody.Therefore , normal female contains one Barrbody. Males only single 'X' chromosome is present which results in absence of Barr body. so this helps in karyotyping studies