The involucrin gene of Old-World monkeys and other higher primates: synapomorphies and parallelisms resulting from the same gene-altering mechanism.

The involucrin gene of platyrrhines and hominoids contains a segment of 10-codon repeats which were added vectorially at the same site in the coding region. We have now cloned and sequenced the involucrin gene of four cercopithecoid monkeys--two macaques (mulatta and fascicularis) and two Cercopithecus monkeys (aethiops and hamlyni). Each gene contains a similar segment of short repeats; some of these were added in a common anthropoid lineage, others were added in a common catarrhine lineage, and still others were added in a common macaque or Cercopithecus lineage. Repeats added before a lineage diverges become synapomorphies in the sister taxa resulting from the divergence. Repeats added independently in different diverged lineages become parallelisms. The synapomorphies are the result of the action of a targeted duplication mechanism acting in a common ancestral lineage, but the parallelisms are the result of the same duplication mechanism transmitted to successively divergent sublineages and acting independently in each.