Answer: You would not notice any difference or any labeled base, because RNA is not used to make DNA.
Step-by-step explanation:
DNA is a molecule that contains the genetic information in all living things. The molecule consists of two strands that wind around each other to form a double helix structure where the strands are joined by hydrogen bonds. It is a nucleotide polymer where each nucleotide consists of a sugar called deoxyribose, a nitrogenous base (which can be adenine, thymine, cytosine or guanine) and a phosphate group (derived from phosphoric acid). What distinguishes one polynucleotide from another, is the nitrogenous base and thus the sequence of DNA is specified by naming only the sequence of its bases. The sequential arrangement of these four bases along the chain is what encodes the genetic information.
Consider that DNA replication is semi-conservative, which means that each strand of the DNA double helix functions as a template for the synthesis of a new complementary strand. This process leads from one starting molecule to two "daughter" molecules, in which each new double helix contains one new and one old strand. Then, if nitrogen tags are incorporated into the DNA, they will register on the old strand of the new DNA molecule.
On the other hand, RNA (ribonucleic acid) is a molecule similar to DNA but has only one strand and consists of a sugar (ribose) and alternating phosphate groups. Attached to each sugar is one of the four bases adenine, uracil, cytosine or guanine. The process of RNA synthesis, called transcription, consists of making a complementary copy of a piece of DNA. During this process, an enzyme called ARN polymerase, adds nucleotides that are complementary to the DNA strand. Then, this new RNA strand has new nucleotides. Thereby, if you examine the DNA strands after completion of DNA replication in the presence of heavy labeled RNA bases, you would not notice any difference or any labeled base, because RNA is not used to make DNA.