ide ▁gas , ▁by ▁cool ing , ▁or ▁with ▁products ▁such ▁as ▁Fly N ap ). ▁Its ▁morph ology ▁is ▁easy ▁to ▁identify ▁once ▁an est het ized . ▁It ▁has ▁a ▁short ▁generation ▁time ▁( about ▁ 1 0 ▁days ▁at ▁room ▁temperature ), ▁so ▁several ▁gener ations ▁can ▁be ▁studied ▁within ▁a ▁few ▁weeks . ▁It ▁has ▁a ▁high ▁f ec und ity ▁( f em ales ▁lay ▁up ▁to ▁ 1 0 0 ▁eggs ▁per ▁day , ▁and ▁perhaps ▁ 2 0 0 0 ▁in ▁a ▁lifetime ). ▁M ales ▁and ▁females ▁are ▁readily ▁distinguished , ▁and ▁vir gin ▁females ▁are ▁easily ▁isolated , ▁facil it ating ▁gen etic ▁crossing . ▁The ▁m ature ▁lar va ▁has ▁giant ▁chrom os om es ▁in ▁the ▁sal iv ary ▁g lands ▁called ▁poly ten e ▁chrom os om es , ▁" p uff s ", ▁which ▁indicate ▁regions ▁of ▁trans cription , ▁hence ▁gene ▁activity . ▁The ▁under - rep lication ▁of ▁r D NA ▁occurs ▁resulting ▁in ▁only ▁ 2 0 % ▁of ▁DNA ▁compared ▁to ▁the ▁brain . ▁Comp are ▁to ▁the ▁ 4 7 %, ▁less ▁r D NA ▁in ▁S arc oph aga ▁bar b ata ▁o var ies . ▁It ▁has ▁only ▁four ▁pairs ▁of ▁chrom os om es ▁– ▁three ▁aut os om es , ▁and ▁one ▁pair ▁of ▁sex ▁chrom os om es . ▁M ales ▁do ▁not ▁show ▁me i otic ▁recom bin ation , ▁facil it ating ▁gen etic ▁studies . ▁Rec ess