English: Figure1. Evolutionary lineage of vertebrate TNNT isoform genes. Data suggested that the three muscle type specific TnT and TnI genes have originated from a TnI-like ancestor gene. A fsTnI-like-fsTnT-like gene pair was generated via gene duplication and further duplicated to form a ssTnI-like-cTnT-like gene pair. Emergence of the cTnI-ssTnT gene pair by a later duplication event gave rise to the three present-day muscle type specific TnI-TnT isoform gene pairs.