le us ▁of ▁the ▁d 4 - 9 5 ▁stra in ▁of ▁P . ▁t etra ure lia ▁contained ▁many ▁more ▁copies ▁of ▁the ▁mut ant ▁gene ▁than ▁in ▁the ▁wild ▁type ▁stra in . ▁This ▁occurs ▁due ▁to ▁the ▁ability ▁of ▁most ▁of ▁the ▁extra ▁pa wn - B ▁gene ▁copies ▁to ▁be ▁her itable ▁independently ▁from ▁the ▁original ▁pa wn - B ▁loc us . ▁Additionally , ▁there ▁is ▁evidence ▁that ▁in ▁the ▁development ▁of ▁the ▁mac ron uc le us ▁between ▁gener ations , ▁there ▁is ▁differential ▁gene ▁dup lication ▁of ▁copies ▁of ▁pa wn - B ▁which ▁causes ▁variable ▁ampl ification ▁of ▁the ▁alle le ▁– ▁between ▁four ▁and ▁twelve ▁times ▁– ▁and ▁heter ogene ity ▁between ▁the ▁copies . ▁This ▁dup lication ▁leads ▁to ▁ampl ification ▁of ▁the ▁gene ▁that ▁suppress es ▁the ▁expression ▁of ▁any ▁non - mut ant ▁pa wn - B ▁lo ci . ▁Dup lication ▁also ▁occurs ▁in ▁the ▁mic ron uc le us , ▁where ▁consider ably ▁higher ▁numbers ▁of ▁copies ▁of ▁the ▁pa wn - B ▁mut ant ▁have ▁been ▁found ▁than ▁the ▁number ▁of ▁copies ▁of ▁the ▁wild - type ▁non - mut ant . ▁Additionally , ▁the ▁number ▁of ▁copies ▁can ▁be ▁decre ased ▁in ▁pro gen y ▁by ▁“ d il uting ” ▁the ▁copies ▁of ▁the ▁mut ant ▁alle le ▁through ▁back cross ing ▁with ▁the ▁wild - type ▁parent , ▁over ▁multiple ▁gener ations . ▁As ▁the ▁number ▁of ▁copies ▁of ▁the ▁pa wn - B ▁mut