▁producing ▁hy brid oma ▁( hy brid ▁cells ▁between ▁an ▁imm ort al ised ▁cell ▁and ▁an ▁ant ib ody ▁producing ▁l ym ph ocy te ), ▁etc . ▁ ▁Ch rom os ome ▁mapping ▁through ▁som atic ▁cell ▁hy brid ization ▁is ▁essentially ▁based ▁on ▁fusion ▁of ▁human ▁and ▁mouse ▁som atic ▁cells . ▁Gener ally , ▁human ▁fib ro cy tes ▁or ▁le uc ocy tes ▁are ▁f used ▁with ▁mouse ▁continuous ▁cell ▁lines . ▁ ▁When ▁human ▁and ▁mouse ▁cells ▁( or ▁cells ▁of ▁any ▁two ▁m amm al ian ▁species ▁or ▁of ▁the ▁same ▁species ) ▁are ▁mixed , ▁sp ont aneous ▁cell ▁fusion ▁occurs ▁at ▁a ▁very ▁low ▁rate ▁( 1 0 - 6 ). ▁Cell ▁fusion ▁is ▁en hanced ▁ 1 0 0 ▁to ▁ 1 0 0 0 ▁times ▁by ▁the ▁addition ▁of ▁ult rav io let ▁in activ ated ▁Send ai ▁( par ain fl uen za ) ▁virus ▁or ▁poly eth yl ene ▁g ly col ▁( PE G ). ▁ ▁These ▁agents ▁ad here ▁to ▁the ▁pl asma ▁memb ran es ▁of ▁cells ▁and ▁alter ▁their ▁properties ▁in ▁such ▁a ▁way ▁that ▁facil it ates ▁their ▁fusion . ▁F usion ▁of ▁two ▁cells ▁produces ▁a ▁heter ok ary on , ▁i . e ., ▁a ▁single ▁hy brid ▁cell ▁with ▁two ▁nuc lei , ▁one ▁from ▁each ▁of ▁the ▁cells ▁entering ▁fusion . ▁Sub sequently , ▁the ▁two ▁nuc lei ▁also ▁f use ▁to ▁yield ▁a ▁hy brid ▁cell ▁with ▁a ▁single ▁nucle