title: Some extrachromosomal circular DNAs from Drosophila embryos are homologous to tandemly repeated genes.
abstract: In Drosophila melanogaster embryos we have identified three classes of extrachromosomal circular DNA molecules homologous to the three main families of tandemly repeated genes, 5 S, rDNA and histone. 5 S genes are present in circular multimeric molecules containing up to 16 copies of the 375(+/- 7) base-pair repeated unit. Circular molecules homologous to rDNA are also multimeric molecules, which contain up to ten copies of the 240 base-pair tandemly repeated sequence of the non-transcribed spacer. The two major genomic classes of histone units (4800 and 5000 bases) are found only as monomeric circular molecules. No circular intermediate of the I transposable element was detected in embryos laid by F1 dysgenic females produced by the I-R system of hybrid dysgenesis. As far as we know, it is the first time that genes have been identified among extrachromosomal circular molecules independently of any specific amplification phenomenon.
mesh_terms: D000818:Animals; D001483:Base Sequence; D004270:DNA, Circular; D004331:Drosophila melanogaster / Q000196:embryology*; D005111:Extrachromosomal Inheritance; D005796:Genes; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004270:DNA, Circular