The involucrin gene of the galago. Existence of a correction process acting on its segment of repeats.

The involucrin gene of the galago, a prosimian, has been cloned and sequenced. The coding region contains a segment of repeats homologous to the segment of repeats in the gene of another prosimian, the lemur, and different from the segments of repeats in the genes of higher primates. The repeats lengths in the two prosimians are similar; and except for a single duplication of a block of repeats in the lemur alone, the number of repeats is the same. However, the nucleotide consensus sequences of the repeats differ between the two species at 3 out of 39 nucleotide positions. The repeats therefore appear to have been modified by a correction process that led toward homogeneity in the repeats of each species while permitting divergence between the two species. The correction process, an example of concerted evolution, has taken place preferentially between adjacent repeats. The numerous differences between the segments of repeats of higher primates and the segments of repeats of lower animals reveal a discontinuity in the evolutionary processes acting on the gene.