The nitrogenous base found in DNA but not in RNA is thymine. Thymine is one of the four bases that make up the genetic code in DNA, along with adenine, cytosine, and guanine. In DNA, thymine pairs specifically with adenine through hydrogen bonding, forming a complementary base pair. In RNA, thymine is replaced by uracil, which pairs with adenine in a similar manner. The presence of thymine in DNA helps to distinguish it from RNA and is important for the stability and integrity of the DNA molecule.
