Thymine-adenine interaction. Computer artwork showing the structure of bound thymine and adenine molecules. Atoms are shown as colour-coded spheres: carbon (green), hydrogen (white), nitrogen (blue) and oxygen (red), with the bonds between them as rods. Thymine and adenine are two of the four nitrogenous bases found in DNA (deoxyribonucleic acid), which form complementary pairs. The positioning of these bases along the RNA and DNA chains is what produces the genetic code. Thymine's complementary base in DNA is adenine. In RNA, thymine is replaced by uracil.