The radioactive labelling of the DNA molecule is possible using radioactive phosphorus and tritium atom. But is it any how possible to label the DNA molecule using a radioactive sulphur atom?
Yes, it is possible, and indeed this was the standard labelling procedure used in early Sanger sequencing.
You synthesise DNA using a deoxynucleotide with a sulphur replacing an oxygen on the α phosphate as shown below. This phosphate forms the phosphodiester link in nucleic acids so the sulphur is incorporated.
response to David's comments
Please note that:
- DNA does not normally contain sulphur.
- This technique is for in vitro labelling of DNA; as far as I am aware it isn't possible to label with sulphur in vivo.