Uracil

Uracil ( /ˈjʊərəsɪl/) one of the four nucleobases in the nucleic acid of RNA that are represented by the letters A, G, C and U. The others are adenine, cytosine, and guanine. In RNA, uracil (U) binds to adenine (A) via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine.