Xa21 FL is splited two entrons flanked one intron by recombination PCR method. Attentively, all of Xa21 DNA clones cover c-Myc with adapter sequence whose size is 48bp, Xa21 FL is equivalent to original Xa21 cDNA add to c-Myc sequence, signed Xa21 cDNA*.

• 所有克隆都包含有48bp的c-Myc及衔接头序列,Xa21 FL就是在原Xa21 cDNA的序列中加入了c-Myc序列,因而标记为Xa21 cDNA,二者实际上完全相同。 Xa21 FL采用重组PCR方法去除中间一段内元拼接两段外元而获得。