Which nitrogenous base is found in RNA but not in DNA?

The nitrogenous base that is found in RNA but not in DNA is uracil. In the structure of RNA, uracil serves as a pyrimidine base that pairs with adenine during the process of transcription. This is a key distinction between RNA and DNA, where thymine is present in place of uracil. The presence of uracil in RNA contributes to the unique properties and functions of RNA, including its role in protein synthesis and genetic coding.

In DNA, adenine pairs with thymine, while in RNA adenine pairs with uracil. The absence of thymine in RNA is a crucial element since it differentiates the structures and functions of these two nucleic acids, impacting their stability and the mechanisms by which they carry genetic information.