Which base is NOT found in RNA?

In RNA, the nitrogenous bases that are typically found include adenine, cytosine, and guanine. However, thymine is not one of those bases. Instead, RNA contains uracil, which replaces thymine in the structure of nucleic acids. The incorporation of uracil in RNA allows for similar pairing with adenine, maintaining the function of code in protein synthesis and other processes. This distinction is key because it sets RNA apart from DNA, which contains thymine instead of uracil. Therefore, identifying thymine as absent in RNA is essential for understanding the differences between these two types of nucleic acids and their roles in biological systems.