▁the ▁symbol ▁in oc l . ▁ ▁T ogether ▁with ▁the ▁In o ▁mut ation , ▁it ▁forms ▁a ▁series ▁of ▁multiple ▁alle les . ▁ ▁The ▁order ▁of ▁domin ance ▁is ▁in o + , ▁in oc l , ▁in o , ▁with ▁in o ▁being ▁the ▁most ▁re cess ive . ▁ ▁Mut ations ▁which ▁are ▁alle lic ▁to ▁In o ▁and ▁cause ▁partial ▁al bin ism ▁are ▁known ▁as ▁Par - ino ▁mut ations ▁in ▁par rot ▁species . ▁ ▁In ▁birds , ▁the ▁co ck ▁has ▁two ▁X ▁chrom os om es ▁and ▁the ▁hen ▁has ▁one ▁X ▁and ▁one ▁Y ▁chrom os ome . ▁ ▁So ▁in ▁h ens ▁wh iche ver ▁alle le ▁is ▁present ▁on ▁the ▁single ▁X ▁chrom os ome ▁is ▁fully ▁expressed ▁in ▁the ▁phen ot ype . ▁ ▁H ens ▁cannot ▁be ▁split ▁for ▁Sex - link ed ▁Clear body ▁( or ▁any ▁other ▁sex - link ed ▁mut ation ). ▁ ▁In ▁co cks , ▁because ▁Sex - link ed ▁Clear body ▁is ▁re cess ive ▁to ▁wild - type ▁and ▁dominant ▁to ▁In o , ▁the ▁Sex - link ed ▁Clear body ▁alle le ▁must ▁be ▁present ▁on ▁both ▁X ▁chrom os om es ▁( hom o zy g ous ) ▁or ▁present ▁on ▁one ▁with ▁an ▁In o ▁alle le ▁on ▁the ▁other ▁to ▁be ▁expressed ▁in ▁the ▁phen ot ype . ▁ ▁C ock s ▁which ▁are ▁heter o zy g ous ▁for ▁Sex - link ed ▁Clear body