WEPO mice have a c-Kit^W/W genotype and lack c-Kit cell surface expression. (A) Lin^- CD34⁺ BM cells from WEPO mice lack expression of c-Kit (CD117) on the cell surface. (B) WEPO mice are homozygous for the W mutation. The DNA product amplified by PCR from genomic DNA from c-Kit⁺, but not from c-Kit^W templates, has an HphI restriction site. After HphI digestion of the PCR product, a 70-bp band indicates a c-Kit⁺ allele (lanes 3, 4), and a 111-bp band indicates a c-Kit^W allele (lanes 2, 3, 5).