icle ▁( w ild ▁type , ▁y 2 - type ). ▁The ▁role ▁of ▁the ▁yellow ▁gene ▁is ▁diverse ▁and ▁is ▁responsible ▁for ▁changes ▁in ▁behaviour , ▁sex - specific ▁re product ive ▁m atur ation ▁and , ▁ep igen etic ▁re programming . ▁The ▁y ▁gene ▁is ▁an ▁ideal ▁gene ▁to ▁study ▁as ▁it ▁is ▁vis ibly ▁clear ▁when ▁an ▁organis im ▁has ▁this ▁gene , ▁making ▁it ▁easier ▁to ▁understand ▁the ▁passage ▁of ▁DNA ▁to ▁off spring . ▁ ▁Gen ome ▁▁ ▁The ▁gen ome ▁of ▁D . ▁mel an og aster ▁( sequ enced ▁in ▁ 2 0 0 0 , ▁and ▁cur ated ▁at ▁the ▁Fly Base ▁database ) ▁contains ▁four ▁pairs ▁of ▁chrom os om es ▁– ▁an ▁X / Y ▁pair , ▁and ▁three ▁aut os om es ▁l abeled ▁ 2 , ▁ 3 , ▁and ▁ 4 . ▁The ▁fourth ▁chrom os ome ▁is ▁so ▁tiny , ▁it ▁is ▁often ▁ignored , ▁aside ▁from ▁its ▁important ▁e y eless ▁gene . ▁The ▁D . ▁mel an og aster ▁sequ enced ▁gen ome ▁of ▁ 1 3 9 . 5 ▁million ▁base ▁pairs ▁has ▁been ▁annot ated ▁and ▁contains ▁around ▁ 1 5 , 6 8 2 ▁gen es ▁according ▁to ▁Ens emble ▁release ▁ 7 3 . ▁More ▁than ▁ 6 0 % ▁of ▁the ▁gen ome ▁appears ▁to ▁be ▁functional ▁non - prote in - c oding ▁DNA ▁involved ▁in ▁gene ▁expression ▁control . ▁Det erm ination ▁of ▁sex ▁in ▁D ros oph ila