title: A variant tandemly repeated nucleotide sequence in Balbiani ring 2 of Chironomus tentans.
abstract: pCtBR2-2 is a genomic clone from Chironomus tentans that hybridized in situ to Balbiani ring 2 (BR2) on salivary gland polytene chromosome IV. DNA sequencing indicated that the insert contained nearly four copies of a 180 bp tandemly repeated nucleotide sequence that was distinctly different from a previously reported BR2 repeat. Sequence titration experiments detected about 70 copies of the 180 bp repeat per haploid genome, which would correspond to approximately 34% of a 37 kb BR2 gene. Each 180 bp repeat included a conserved 90 bp segment whose sequence was internally nonrepeating (INR), and a variable 90 bp repeated (R) segment comprised of three 30 bp repeats that may have evolved from a 9 bp consensus sequence. Results presented here raise the distinct possibility that other BR genes may contain significantly different repeated sequences that have not been identified.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002683:Chironomidae / Q000235:genetics*; D002874:Chromosome Mapping; D004247:DNA / Q000032:analysis*; D004175:Diptera / Q000235:genetics*; D015870:Gene Expression; D009693:Nucleic Acid Hybridization; D012313:RNA / Q000032:analysis; D012091:Repetitive Sequences, Nucleic Acid; D012469:Salivary Glands / Q000032:analysis
chemical_list: D012313:RNA; D004247:DNA