<prompt> DNA labelling is done by usingTc-99P-321-131Co-60  <response>: 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. 