Final answer:
To make DNA in a laboratory radioactive, you need to incorporate radioactive nucleotides.
Step-by-step explanation:
In order to ensure that DNA made in a laboratory is radioactive, one must incorporate radioactive nucleotides into the DNA. Radioactive nucleotides, such as radioactively labeled dATP or [^32P]dCTP, can be used during the polymerase chain reaction (PCR) or DNA synthesis process. These nucleotides contain radioactive isotopes that emit radiation, allowing the DNA to be detected and traced.
Learn more about Radioactive nucleotides