A REPETITIVE DNA-SEQUENCE ASSOCIATED WITH THE CENTROMERES OF CHIRONOMUS-PALLIDIVITTATUS

A clone containing centromere-associated DNA from Chironomus pallidivi ttatus was obtained by microdissection-microcloning. It hybridizes to the centromeric end of one chromosome and exclusively to regions in th e three remaining, metacentric chromosomes to which centromeres have p reviously been localized on cytological grounds. In the metacentric po sitions the hybridization can be assigned to thin bands. The clone con tains 155bp tandem repeats and short flanking regions represented in a ll of the centromeres. Titration experiments show that the four centro meres together contain 200kb of 155bp repeat per genome. In a line of tissue culture cells the amounts are increased by a factor 1.5 - 2, re sulting in proportionately extended arrays of tandem repeats. Each rep eat contains two invertrepeats surrounding a region containing only AT base pairs, a feature with some similarity to functionally essential elements in the Saccharomyces cerevisiae centromere.