[too rz duh fawrs, -fohrs; French toor duh fawrs] /ËtÊÉrz dÉ ËfÉrs, -ËfoÊrs; French tur dÉ ËfÉrs/ (Show IPA) 1. an exceptional achievement by an artist, author, or the like, that is unlikely to be equaled by that person or anyone else; stroke of genius: Herman Melville's Moby Dick was a tour de force. 2. a particularly adroit maneuver or technique in handling a difficult situation:
edit Nucleobases. Purines make up two of the four nucleobases in DNA and RNA: adenine and guanine. Pyramidines make up the other bases in DNA and RNA: cytosine, thymine (in DNA) and uracil (in RNA).
In nucleic acids, nitrogenous bases contain either one ring or two fused rings. Purines are double-ring nitrogenous bases found in nature and include adenine and guanine. Thymine, cytosine and uracil are pyrimidines, single-ring nitrogenous bases found in nature.The sugar and nitrogenous base present in a nucleotide define the nucleotide and its functional role.urines are double-ring nitrogenous bases found in nature and include adenine and guanine. Thymine, cytosine and uracil are pyrimidines, single-ring nitrogenous bases found in nature. The sugar and nitrogenous base present in a nucleotide define the nucleotide and its functional role.