from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A pyrimidine base, C4H4N2O2, that is an essential constituent of RNA.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. One of the bases of RNA. It pairs with adenine and is symbolised by U.
from The Century Dictionary and Cyclopedia
- n. A colorless compound, prepared by the action of hydrochloric acid on methylmercapto-uracil. It crystallizes in spherical masses of minute needles and melts at 338° C.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine
Adenine and guanine are fused five - and six-membered purines, while cytosine and thymine are six-membered rings called uracil (U), replaces thymine in RNA.
For 40 years, efforts to understand the prebiotic synthesis of the ribonucleotide building blocks of RNA have been based on the assumption that they must have assembled from their three molecular components: a nucleobase (which can be adenine, guanine, cytosine or uracil), a ribose sugar and phosphate.
Of the many difficulties encountered by those in the field, the most frustrating has been the failure to find any way of properly joining the pyrimidine nucleobases — cytosine and uracil — to ribose (Fig. 1a).
The interface properties of the protein-RNA complexes reveal the diverse nature of the binding sites. van der Waals contacts played a more prevalent role than hydrogen bond contacts, and preferential binding to guanine and uracil was observed.
A number of different sensors have been developed, based on triggers that include direct DNA damage, the inactivation of bacterial spores and bacteriophages, photochemical reactions involving vitamin D photosynthesis, and the accumulation of polycrystalline uracil.
Hence, it is more efficient to quickly synthesize uracil and quickly synthesize labile RNAs.
For example, suppose one wishes to explain why DNA has thymine and why messenger RNA, transfer RNA, and ribosomal RNA have uracil.
Uracil is cheaper to synthesize than thymine, because thymine has a methyl group that uracil lacks.
Carbon isotope ratios for uracil and xanthine of δ13C = + 44.5‰ and + 37.7‰, respectively, indicate a non-terrestrial origin for these compounds.
Briefly, this method involves digesting the nucleic acid with T1 RNAse, which cuts after every guanine residue, followed by another digestion with an enzyme that cuts after the adenine, cytosine or uracil residues.