Hydroxymethyluracil in eukaryote DNA: a natural feature of the pyrrophyta (dinoflagellates).

Analysis of the DNA of several diverse dinoflagellates and other algae has revealed that the presence of the base hydroxymethyluracil (HOMeU) is a feature common among the DNA's of dinoflagellates; this base has not been found in any other group of eukaryotes that has been examined. Among examined members of the dinoflagellates, the ratio of the base pairs HOMeU-A to T-A, where A is adenine and T is thymine, ranges from 0.14 to 2.13. In addition to hydroxymethyluracil, the DNA of one dinoflagellate contains methylcytosine, and that of another contains methyladenine, while the DNA of other dinoflagellates contains no detectable amounts of either of these two bases.