Puromycin dihydrochloride is widely used as a selection agent in cell culture systems. It is effective in selecting transfected eukaryotic cells that have been engineered with resistance genes, such as the pac gene, which encodes puromycin N-acetyl-transferase. When added to cell cultures, it kills non-resistant cells by inhibiting protein synthesis, specifically by causing premature termination during translation. This makes it a valuable tool in stable cell line development, gene expression studies, and CRISPR/Cas9 genome editing workflows. Its rapid action—typically killing sensitive cells within 2–5 days—allows for quick selection and expansion of desired cell populations. It is also used in microbial selection and in studies involving RNA metabolism due to its structural similarity to aminoacyl-tRNA.