Exclusion of repetitive DNA elements from gnathostome Hox clusters.

The Hox gene clusters of gnathostomes have a strong tendency to exclude repetitive DNA elements. In contrast, no such trend can be found in the Hox gene clusters of protostomes. Repeats \invade" the gnathostome Hox clusters from the 5’ and 3’ ends while the core of the clusters remains virtually free of repetitive DNA.