Figure 1

Evolutionary scenarios for proteins containing Vertebrate domains. a) The Old domain can be found in combination with the Vertebrate domain as well as separate, but the Vertebrate domain is always found in combination with the Old domain; 118 different Vertebrate domains, 148 different Old domains. b) Both Old and Vertebrate domains can be found combined and separately; 11 different Vertebrate domains, 23 different Old domains. c) Vertebrate domains that are never found in combination with Old domains; 234 different Vertebrate domains.