Rodriguez de Cordoba et al. (1994) used a human C4BPB cDNA probe to isolate and characterize a genomic DNA fragment that included the murine C4BPB gene. They found that it is present in single copy and maps close to the murine homolog of C4BPA on chromosome 1. However, in several inbred strains of Mus musculus and in Mus spretus, they demonstrated 2 inphase stop codons that are incompatible with the expression of a functional C4BPB polypeptide. It appeared that the loss of a functional C4BPB gene was a relatively recent event in the evolution of the mouse. Since the genetic change had become fixed, the mice lacking the C4BPB polypeptide may have enjoyed some kind of selective advantage.there are 7 genes in the regulator of complement activation (RCA) gene cluster: C4BPA, C4BPB, MCP, CR1, CR2, DAF, and CFH. Hillarp et al.