▁une qual ▁crossing ▁over , ▁hom olog ous ▁chrom os om es ▁exchange ▁une ven ▁port ions ▁of ▁their ▁DNA . ▁This ▁can ▁lead ▁to ▁the ▁transfer ▁of ▁one ▁chrom os ome ' s ▁gene ▁to ▁the ▁other ▁chrom os ome , ▁leaving ▁two ▁of ▁the ▁same ▁gene ▁on ▁one ▁chrom os ome , ▁and ▁no ▁copies ▁of ▁the ▁gene ▁on ▁the ▁other ▁chrom os ome . ▁Non - hom olog ous ▁dup lications ▁result ▁from ▁rep lication ▁errors ▁that ▁shift ▁the ▁gene ▁of ▁interest ▁into ▁a ▁new ▁position . ▁A ▁tan dem ▁dup lication ▁then ▁occurs , ▁creating ▁a ▁chrom os ome ▁with ▁two ▁copies ▁of ▁the ▁same ▁gene . ▁Figure ▁ 1 ▁to ▁the ▁left ▁provides ▁a ▁good ▁visual ▁explanation ▁of ▁these ▁three ▁mechan isms . ▁As ▁the ▁gen ome ▁is ▁rep licated ▁over ▁many ▁gener ations , ▁the ▁redundant ▁gene ' s ▁function ▁will ▁most ▁likely ▁evol ve ▁due ▁to ▁Gen etic ▁dr ift . ▁This ▁means ▁that ▁the ▁gene ▁will ▁ac quire ▁mut ations ▁that ▁change ▁the ▁overall ▁function . ▁The ▁three ▁mechan isms ▁of ▁functional ▁different iation ▁in ▁gen es ▁are ▁non function al ization ▁( or ▁gene ▁loss ), ▁ne of unction al ization ▁and ▁sub function al ization . ▁ ▁During ▁non function al ization , ▁or ▁deg ener ation / g ene ▁loss , ▁one ▁copy ▁of ▁the ▁dup licated ▁gene ▁acqu ires ▁mut ations ▁that ▁render ▁it ▁in active ▁or ▁silent . ▁At ▁this ▁time , ▁the ▁gene ▁has ▁no ▁function ▁and ▁is ▁called