DNA labelling is done by using

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.