Sequence Homology within Families of Drosophila melanogaster Middle Repetitive DNA
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Excerpt
A large fraction of the DNA in higher organisms is repeated 10–100,000 times per nucleus. Although the function of this middle repetitive DNA is unknown, there have been proposals that it allows complex patterns of gene expression (reviewed in Davidson and Britten 1973), chromosome rearrangements (Lee 1975), or specific chromosomal associations such as ectopic pairing (Finnegan et al.; Rubin; both this volume). All of these proposals require that homologous repeats have an identical function so that, for example, the repeats of one sequence may all be recognized and bound by the same repressor protein. If two repeats have such an identical function, then there must be a limit to the difference between their base sequences. Thus the evidence that middle repetitive DNA of many organisms has a broad range of sequence homology (Britten and Davidson 1971; Davidson and Britten 1973) is significant for these proposals because it suggests either that...
