DNA structures common for chironomid telomeres terminating with complex repeats

Tandem repeats, 340 bp long, have been shown to terminate the chromosomes i n Chironomus pallidivittatus and similar DNA may be used for this purpose b y related insects. In view of the importance of Chironomus in telomere stud ies, representing in principle a third system after short repeats and Droso phila telomeric retrotransposons, we have investigated the related Chironom us dilutus, to learn what DNA structures are conserved at the chromosome en ds. Interspersed sub-repeats in the telomeric repeats, which contain a long palindrome, and a zone of about 100 bp of relatively constant subtelomeric DNA towards the junction to the telomeric DNA, are characteristic for C. d ilutus as for previously investigated species. C. dilutus has similar subte lomeric DNA at all chromosome ends, but typical telomeric repeats in only s even of the pairs since the eighth telocentric pair contains centromere-spe cific repeats.