The full length sequence of the human ZP2 gene in BAC RP11-1023A8 is modified by replacing the corresponding mouse exons encoding amino acids 18-156 (bp 1 in exon 2 to bp 150 in exon 5) for the human amino acids 22-161 (bp 1 in exon 2 to bp 152 in exon 5) at the N-terminus of gene. (J:215794)