I am cloning 3.4kb human genome DNA into a 8.4kb vector.Isolate some plasmids. Recut,then 3.4kb bands appear. But sequencing shows it is not 3.4kb human DNA,it is a unknown fragment. Strangely,the size is same as 3.4kb! What happen? Any idea to eliminate recombination ? The competent cells used are Invitrogen ElectroMAX™ DH10B™ T1 Phage- Resistant Competent Cells Cat. No. 12033-015.