This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Types of Genetic Disorders, Subject name: Pediatrics
F body is? 
Select and explain. 
A. Y chromatin, B. X chromatin, C. Chromosome 1, D. Chromosome 21
A: Y chromatin
Answer: A: Y chromatin 
Explanation: Quinacrine, a fluorescence dye, binds strongly to Y chromosome forming a bright fluorescent spot (F body).