Which nitrogenous base is unique to RNA?

Uracil is a nitrogenous base that is unique to RNA, setting it apart from DNA. In RNA, uracil replaces thymine, which is present in DNA. This distinction is important in the structure and function of nucleic acids.

During transcription, RNA polymerase synthesizes RNA by pairing the base adenine with uracil instead of thymine as found in DNA. Uracil's structure allows it to fulfill the same pairing function as thymine, but its presence is exclusive to RNA, making it a defining characteristic of ribonucleic acid. Thus, recognizing uracil as the base that is unique to RNA enhances comprehension of molecular biology and the differentiation between RNA and DNA.