Final answer:
Uracil is a nitrogenous base found exclusively in RNA, where it pairs with adenine. It is one of the structural components that distinguish RNA from DNA, which contains thymine instead.
Step-by-step explanation:
Uracil is a nitrogenous base found in RNA (ribonucleic acid). Unlike DNA, which contains the base thymine, RNA incorporates uracil in its place. This distinction is key in understanding the differences between RNA and DNA. RNA is typically a single-stranded molecule and includes other nucleotides with adenine, guanine, and cytosine, but the presence of uracil is one of the main structural differences when compared to DNA.
RNA plays a crucial role in various cellular processes, including protein synthesis, where it assumes the forms of mRNA, tRNA, and rRNA. Each form of RNA has a specific function, and tRNA, for instance, can be recognized because it is relatively small, contains uracil, and most of its forms are covalently bound to amino acids.
To summarize, uracil is exclusively found in RNA, serving as a base pair with adenine, and its presence is one of the defining factors that separate RNA from DNA structurally and functionally.