▁human ▁disease . ▁M ice ▁are ▁a ▁useful ▁model ▁for ▁gen etic ▁manip ulation ▁and ▁research , ▁as ▁their ▁t issues ▁and ▁org ans ▁are ▁similar ▁to ▁that ▁of ▁a ▁human ▁and ▁they ▁carry ▁virt ually ▁all ▁the ▁same ▁gen es ▁that ▁operate ▁in ▁humans . ▁They ▁also ▁have ▁advantages ▁over ▁other ▁m amm als , ▁in ▁regards ▁to ▁research , ▁in ▁that ▁they ▁are ▁available ▁in ▁hundreds ▁of ▁gen et ically ▁hom ogeneous ▁stra ins . ▁Also , ▁due ▁to ▁their ▁size , ▁they ▁can ▁be ▁kept ▁and ▁hous ed ▁in ▁large ▁numbers , ▁reducing ▁the ▁cost ▁of ▁research ▁and ▁experiments . ▁The ▁most ▁common ▁type ▁is ▁the ▁knock out ▁mouse , ▁where ▁the ▁activity ▁of ▁a ▁single ▁( or ▁in ▁some ▁cases ▁multiple ) ▁gen es ▁are ▁removed . ▁They ▁have ▁been ▁used ▁to ▁study ▁and ▁model ▁ob es ity , ▁heart ▁disease , ▁di ab etes , ▁ar th rit is , ▁subst ance ▁ab use , ▁anx iety , ▁ag ing ▁and ▁Park inson ▁disease . ▁Trans gen ic ▁m ice ▁generated ▁to ▁carry ▁cl oned ▁on c ogen es ▁and ▁knock out ▁m ice ▁lack ing ▁tum or ▁suppress ing ▁gen es ▁have ▁provided ▁good ▁models ▁for ▁human ▁cancer . ▁H undred s ▁of ▁these ▁on com ice ▁have ▁been ▁developed ▁covering ▁a ▁wide ▁range ▁of ▁can cers ▁affect ing ▁most ▁org ans ▁of ▁the ▁body ▁and ▁they ▁are ▁being ▁ref ined ▁to ▁become ▁more ▁representative ▁of ▁human ▁cancer . ▁The ▁disease ▁sympt oms ▁and ▁potential ▁dru gs