Homozygous null embryos die prior to the formation of a blastocyst. Mice heterozygous for some point mutations show pigment defects affecting the feet and tail. However the heterozygotes show a normal development of the hematopoietic system. Heterozygous missense mutations of Rps19 show a mild macrocytic anemia reflecting the fact that mutations causes a hypomorphic allele rather than true happloinsufficiency. This evidence concerns the gene RPS19 and anemia.