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: Biochemistry
DNA labelling is done by using 
Select and explain. 
A. Tc-99, B. P-32, C. 1-131, D. Co-60
B: P-32
Answer: B: P-32 
Explanation: Ans. is 'b' i.e., P-32 The simplest form of labelling DNA is by 5'- or 3'- end labelling.5`-end - labelling involves a phophate transfer or exchange reaction where the 5' - phosphate of the DNA to be used as the probe is removed and in its place a labelled phasphate, usually P32 is added.In 3'-end-labelling, labelled dNTP (ATP or biotin-labelled dNTP) is added to 3' end of DNA by enzyme terminal transferase.