Table 1.

Summary of gene targeting efficiencies in different ES cell lines

ESC line	Integration frequency*	No. clones analyzed	Homologous recombinants†	Euploid recombinants‡
W4	250	716	1/26	0 (19)
R1	400	817	1/63	0 (12)
J1	1,500	444	1/3.2	0 (14)
E14	1,500	672	1/2.4	42 (12)

^*G418^r clones/10⁷ cells. 

^†Frequency of integration events at the Stat3 locus among G418^r colonies. 

^‡Percentage of euploid targeted clones and the number assayed.