TERMINAL LONG TANDEM REPEATS IN CHROMOSOMES FROM CHIRONOMUS-PALLIDIVITTATUS

We provide evidence that a chromosome end in the dipteran Chironomus p allidivittatus contains 340-bp tandem repeats reaching the extreme ter minus of the chromosome. After adding synthetic oligonucleotide tails to DNA extracted from the microdissected right end of the fourth chrom osome, we could demonstrate that the blocks of repeats were tailed at only one end, the chromosome terminus, the interior of the arrays bein g unavailable for tailing. Using PCR, we furthermore showed that the a dded tails were connected to 340-bp repeat DNA directly, i.e., without intervening DNA of any other kind. The tailed repeats belong to a sub family previously known to be the most peripheral one of the different types of 340-bp units. Using plasmid controls, we could also make cer tain that we did not amplify rare or nonrepresentative DNA termini.