Analysis of the constancy of DNA sequences during development and evolution of the nematode Caenorhabditis elegans

In order to test for the occurrence of rearrangements in DNA during development and to assess the rate of DNA divergence during evolution, we have compared restriction fragments derived from DNA from four sources: sperm cells and somatic tissues of one strain of the nematode Caenorhabditis elegans, somatic tissues of a second strain of the same species, and whole animals of a closely related species. Restriction fragments were detected by hybridizing radioactive cloned fragments to restriction digests that had been fractionated by size on agarose gels and transferred to nitrocellulose sheets. In this way, approximately 50 BamHI restriction fragments were visualized and compared. Fragments from sperm and somatic DNAs were found to be identical; 15% differed in size between the two strains. Little cross homology was found between the two species. We conclude that, if rearrangements occur in C. elegans DNA during development, they must affect fewer than a few percent of the restriction fragments or restriction sites. The difference found between the two strains and the two species is surprisingly great.