Fig. 3. Linkage of a kinase mutation in mps1 to ncp. (A) Genetic and physical map of ncp region indicating genomic DNA, YAC clone, cosmids, and cDNAs. Numbers in parentheses represent recombination events from 1,751 meioses in regions between ncp and linked genetic markers. (B,C) Mutational analysis of mps1. Sequencing of cDNAs from ncp and several wild-type strains revealed a unique thymidine to adenosine mutation that altered isoleucine-843 to lysine (red). A portion of the highly conserved carboxyl terminal kinase domain of Mps1 containing the I843K mutation is shown. This isoleucine is highly conserved among vertebrates. Thus, a mutation in mps1 is associated with the ncp regeneration defect.