DO Supplement -Ura is a specialized nutrient mixture for synthetic dropout media in yeast and fungal cell culture. It provides all required amino acids, vitamins, and other growth factors except uracil, enabling the creation of uracil-deficient selective media. This supplement is used to select for transformants carrying the URA3 gene, which complements uracil auxotrophy in host strains. Only cells with the plasmid (capable of uracil biosynthesis) can grow on such media, promoting plasmid stability. Commonly utilized in molecular biology and genetic engineering for strain construction, transformation selection, and gene expression studies, particularly in Saccharomyces cerevisiae.