Genetic mapping and positional cloning of sublytic. (A) Genetic linkage on chromosome 7 was established by bulk segregation analysis mapping using 26 mice (10 anemic and 16 nonanemic mice). (B) A single nucleotide transition (T863C) was detected in Atp4a. This mutation results in a serine to proline change at position 282 of the encoded gastric H⁺,K⁺-ATPase α subunit.