▁true ▁Bil ater a , ▁making ▁these ▁gen es ▁pre - P ale oz o ic . ▁It ▁is ▁accepted ▁that ▁the ▁three ▁major ▁animal ▁AN TP - class ▁clusters , ▁H ox , ▁Para H ox , ▁and ▁NK ▁( Meta H ox ), ▁are ▁the ▁result ▁of ▁segment al ▁dup lications . ▁A ▁first ▁dup lication ▁created ▁Meta H ox ▁and ▁Pro to H ox , ▁the ▁latter ▁of ▁which ▁later ▁dup licated ▁into ▁H ox ▁and ▁Para H ox . ▁The ▁clusters ▁themselves ▁were ▁created ▁by ▁tan dem ▁dup lications ▁of ▁a ▁single ▁AN TP - class ▁home obox ▁gene . ▁Gene ▁dup lication ▁followed ▁by ▁ne of unction al ization ▁is ▁responsible ▁for ▁the ▁many ▁home obox ▁gen es ▁found ▁in ▁e uk ary otes . ▁Com parison ▁of ▁home obox ▁gen es ▁and ▁gene ▁clusters ▁has ▁been ▁used ▁to ▁understand ▁the ▁evolution ▁of ▁gen ome ▁structure ▁and ▁body ▁morph ology ▁throughout ▁met az o ans . ▁ ▁Types ▁of ▁home obox ▁gen es ▁ ▁H ox ▁gen es ▁ ▁H ox ▁gen es ▁are ▁the ▁most ▁commonly ▁known ▁subset ▁of ▁home obox ▁gen es . ▁They ▁are ▁essential ▁met az o an ▁gen es ▁that ▁determine ▁the ▁identity ▁of ▁emb ry onic ▁regions ▁along ▁the ▁anterior - post er ior ▁axis . ▁ ▁The ▁first ▁verte br ate ▁H ox ▁gene ▁was ▁isolated ▁in ▁X en opus ▁by ▁Edward ▁De ▁Robert is ▁and ▁colle agues ▁in ▁ 1 9 8 4 . ▁The ▁main ▁interest ▁in ▁this ▁set