▁gene - one ▁en zym e " ▁hypothesis ▁that ▁was ▁originally ▁introduced ▁by ▁French ▁bi ologist ▁Luci en ▁Cu é not ▁in ▁ 1 9 0 3 . ▁This ▁hypothesis ▁shift ed ▁future ▁research ▁regarding ▁ple iot ropy ▁towards ▁how ▁a ▁single ▁gene ▁can ▁produce ▁various ▁phen ot ypes . ▁ ▁In ▁the ▁mid - 1 9 5 0 s ▁Richard ▁Gold sch midt ▁and ▁Ernst ▁Had orn , ▁through ▁separate ▁individual ▁research , ▁rein for ced ▁the ▁fault iness ▁of ▁" gen u ine " ▁ple iot ropy . ▁A ▁few ▁years ▁later , ▁Had orn ▁partition ed ▁ple iot ropy ▁into ▁a ▁" m osa ic " ▁model ▁( which ▁states ▁that ▁one ▁loc us ▁directly ▁affect s ▁two ▁phen ot yp ic ▁tra its ) ▁and ▁a ▁" rel ational " ▁model ▁( which ▁is ▁analog ous ▁to ▁" sp ur ious " ▁ple iot ropy ). ▁These ▁terms ▁are ▁no ▁longer ▁in ▁use ▁but ▁have ▁contributed ▁to ▁the ▁current ▁understanding ▁of ▁ple iot ropy . ▁ ▁By ▁accepting ▁the ▁one ▁gene - one ▁en zym e ▁hypothesis , ▁scient ists ▁instead ▁focused ▁on ▁how ▁un cou ple d ▁phen ot yp ic ▁tra its ▁can ▁be ▁affected ▁by ▁gen etic ▁recom bin ation ▁and ▁mut ations , ▁applying ▁it ▁to ▁populations ▁and ▁evolution . ▁This ▁view ▁of ▁ple iot ropy , ▁" univers al ▁ple iot ropy ", ▁defined ▁as ▁loc us ▁mut ations ▁being ▁capable ▁of ▁affect ing ▁essentially ▁all ▁tra its , ▁was ▁first ▁imp lied ▁by