Which of these nitrogenous bases may be found in RNA but not in DNA?

Uracil is the nitrogenous base that is found in RNA but not in DNA. In the chemical structure of nucleic acids, uracil replaces thymine, which is present in DNA. RNA is typically single-stranded, and the use of uracil allows for the structural variations that facilitate its various functions, such as coding, decoding, regulation, and expression of genes.

The presence of uracil in RNA is significant not only because of its distinct role but also because it helps distinguish RNA from DNA, which is essential for understanding how genetic information is transmitted and used within biological systems. The other bases—adenine, thymine, and guanine—are all found in DNA as well as RNA, thus underscoring the unique role of uracil in the context of RNA.