The involucrin genes of the white-fronted capuchin and cottontop tamarin: the platyrrhine middle region.

In all anthropoid species, the coding region of the involucrin gene contains a segment of short tandem repeats that were added sequentially, beginning in a common anthropoid ancestor. The involucrin coding region of each of two platyrrhine species, the white-fronted capuchin (Cebus albifrons) and the cottontop tamarin (Saguinus oedipus), has now been cloned and sequenced. These genes share with the genes of the catarrhines the repeats added in the common anthropoid lineage (the early region). After their divergence, the platyrrhines, like the catarrhines, continued to add repeats vectorially 5' of the early region, to form a middle region. The mechanism that was established in the common anthropoid lineage for the addition of repeats at a definite site in the coding region was transmitted to both platyrrhines and catarrhines, enabling each to generate its middle region independently. The process of vectorial repeat addition continued in two platyrrhine sublineages after their divergence from each other.