The chordate ancestor possessed a single copy of the Brachyury gene for notochord acquisition.
Jun InoueYuuri YasuokaHiroki TakahashiNoriyuki SatohPublished in: Zoological letters (2017)
Our results thus suggest that, in the common ancestor of chordates, a single copy of Brachyury acquired two expression domains and that the duplication was not involved in the acquisition of the notochord. However, in relation to regulatory mechanisms, both possibilities-namely a single copy with two domains and two copies with different domains-should be considered in future studies of Brachyury.