title: Selective incorporation of thymidine in the organelle DNA of Polytoma obtusum.
abstract: Polytoma obtusum was found to selectively incorporate exogenous thymidine into its leukoplast DNA. The nuclear DNA was unable to incorporate [3H]thymidine, although both DNA species could be labeled with radioactive adenine with similar efficiencies. The mitochondrial DNA (mitDNA), which had a buoyant density of 1.714 g/ml and was banded slightly on the heavier side of the nuclear DNA peak, was also found to incorporate a small amount of [3H]thymidine. These observations suggest that P. obtusum lack cytoplasmic thymidine kinase, whereas the enzyme is present in both leukoplast and mitochondria.
mesh_terms: D000225:Adenine / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis*; D004272:DNA, Mitochondrial / Q000096:biosynthesis; D056890:Eukaryota / Q000378:metabolism* / Q000648:ultrastructure; D008928:Mitochondria / Q000201:enzymology; D009940:Organoids / Q000201:enzymology / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism*; D013937:Thymidine Kinase / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D004247:DNA; D013937:Thymidine Kinase; D000225:Adenine; D013936:Thymidine