Researchers at UT Dallas used an enzyme called TdT to create unique genetic "fingerprints" inside living cells—a breakthrough in biosecurity that could help biotech companies verify cell identity and prevent counterfeiting. The technique, published in Advanced Science, increases randomness in DNA repair to generate one-of-a-kind markers. This cropped image shows a key step—Pol X’s role in the process. [Source: Figure 1, TdT (1D) PUF/Advanced Science]