engleski

Unusual organization of DNA sequences in Tribolium madens heterochromatin

Two highly abundant satellite DNAs from an insect, Tribolium madens (Coleoptera) are distributed over the whole centromeric heterochromatin of all chromosomes. Both satellites form large clusters, ranging in size from 150 kb up to several Mb, but within the clusters they are in the form of highly interspersed, short homogeneous arrays which vary in size with a lowest length limit of only few kb. The longest homogeneous array of a single satellite is relatively short, up to 70 kb. Gaps on DNA fibers that did not hybridize with either of the two satellites are infrequent and short, the longest up to 22 kb, indicating a relatively small contribution of non-satellite sequences in T. madens heterochromatin. No chromosome specificity in sequence organization could be observed. Unusual interspersed organization of short arrays of both satellites together with some other uncharacterized sequences spans regions of centromeric hetorochromatin of almost 10 Mb on average, and probably includes a functional centromere, as well. The results indicate that if we do not assume some specific sequences interspersed with satellite DNAs, region of the functional centromere could not be distinguished from the centromeric heterochromatin of T. madens chromosomes as a whole.

interspersed organization ; DNA fibers ; extended chromosomes ; two color FISH

nije evidentirano