Mouse colonies of two other monogenetic autosomal recessive disorders, sickle cell anemia (carrying a point mutation in the β -globin gene[18]; and Niemann-Pick Type C disease (carrying a point mutation in Npc1 gene [19,20]) yielded homozygous mutant progeny at rates between 21–22% (Fig 5B). Here, NPC1 is linked to Niemann-Pick disease type C.