est nut - like ▁to ▁silver ▁black - like . ▁L ighter ▁eyes ▁can ▁help ▁with ▁identification . ▁ ▁In herit ance ▁and ▁expression ▁ ▁The ▁cre am ▁loc us ▁is ▁on ▁ex on ▁ 2 ▁of ▁the ▁M AT P ▁gene ; ▁a ▁single ▁nucle ot ide ▁polym orphism ▁results ▁in ▁an ▁as part ic ▁acid - to - as par agine ▁substitution ▁( N 1 5 3 D ). ▁The ▁DNA ▁test ▁offered ▁by ▁various ▁labor ator ies ▁detect s ▁this ▁mut ation . ▁The ▁M AT P ▁gene ▁enc odes ▁a ▁protein ▁illustrated ▁to ▁have ▁roles ▁in ▁mel an ogen esis ▁in ▁humans , ▁m ice , ▁and ▁med aka . ▁M ice ▁affected ▁by ▁a ▁condition ▁hom olog ous ▁to ▁cre am ▁exhib it ▁irregular ly ▁sh aped ▁mel anos om es , ▁which ▁are ▁the ▁organ elles ▁within ▁mel an ocy tes ▁that ▁directly ▁produce ▁p ig ment . ▁▁ ▁Gen es ▁in ▁horses ▁such ▁as ▁Frame ▁and ▁Sab ino 1 ▁produce ▁white ▁spot ting ▁by ▁interrupt ing ▁or ▁limit ing ▁the ▁migration ▁of ▁mel an ocy tes ▁from ▁the ▁neural ▁cr est , ▁while ▁the ▁cre am ▁mut ation ▁affect s ▁the ▁nature ▁of ▁the ▁p ig ments ▁produced ▁by ▁mel an ocy tes . ▁Therefore ▁the ▁skin , ▁eyes , ▁and ▁hair ▁of ▁horses ▁with ▁the ▁cre am ▁mut ation ▁do ▁not ▁lack ▁mel an ocy tes , ▁mel anos om es , ▁or ▁mel an ins , ▁but ▁rather ▁exhib it ▁hyp om el an