Evidence for nonrandom alterations in a fraction of the highly repetitive DNA of a eukaryote.

Although the DNA of the red crab Geryon quinquedens has no patent satellites, a large fraction (approximately 40%) is highly repetitive. Treatment of total DNA by Hind III produces fragments comprising 5-6% of the genome. While the sizes of some of these fragments form an arithmetic series based on an 81 bp repeating unit, the amounts of the multimers differ significantly from distributions observed for multimeric series in the DNAs of other eukaryotes. In red crab DNA, the amounts of some of the multimers suggest that they may have undergone as much as four times the divergence as the others. Other data, however, are more compatible with the conclusion that there has been selective amplification of segments of highly repeated DNA which results in the enhanced amount of specific multimers. These results indicate the presence of a nonrandom process in the evolution of the highly repetitive DNA. Selective mutation alone seems insufficient to explain these results.