Table 1. Summary of targeting efficiency of mutations generated in the BRCA1 gene.

Mutation	Codon	Nucleotide	Amino acid change	Targeting frequencya		Clones confirmed by sequencing
				Step 1	Step 2
delt A	339	1129	Stop 340	1/65	1/68	3/3
G to T	1495	4603	Arg to Met	1/32	1/32	3/3
G to A	1823	5586	Ala to Thr	1/840	1/1003	2/2

^aNumber of PCR positive clones/number of electroporated cells.