growth of a strain of bacillus subtilis that requires uracil , thymine , adenine , and tryptophan in the presence of 5-fluorouracil ( fu ) results in the synthesis of ribonucleic acid ( rna ) and ribosomes in which 55 to 65 % of the rna uracil has been replaced by the fluorine derivative .
C0040087
thymine
C0041917
uracil