This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc. (W.B.C), Subject name: Pathology
BCR-ABL fusion gene is detected by? 
Select and explain. 
A. Flow cytometry, B. FISH, C. Karyotyping, D. RT-PCR
B: FISH
Answer: B: FISH 
Explanation: Ans. (b) FISH(Ref: Robbins 9th/pg 616-618)Flow cytometry: is used for immunophenotyping in Leukemias & LymphomasFISH- used for detecting submicroscopic chromosomal aberrations of BCR-ABL fusionKaryotyping: Used for detecting chromosomal defects of at least 5 mb size (low sensitivity)RT-PCR: used for quantitative DNA estimation