A pyrimidine base that replaces thymine in RNA, where it pairs with adenine during transcription and translation; also a constituent of the nucleoside uridine. Uracil is one of the four standard RNA nucleobases, and its presence distinguishes RNA from DNA in molecular biology. In food-related biotechnology, uracil metabolism underpins yeast genetics — ura3 auxotrophic markers are workhorses of strain engineering — and RNA-based detection methods for foodborne pathogens rely on uracil-containing sequences. Understanding nucleobase chemistry supports PCR diagnostics, starter-culture improvement, and the analysis of nucleic acids in foods.