Pedigree of the NCCD Beagle family. Squares and circles represent male and female individuals respectively. Shaded symbols represent NCCD cases (all deceased). The distribution and number of affected individuals is consistent with an autosomal recessive mode of inheritance. Homozygous wild-type individuals are represented as wt/wt, heterozygotes as wt/del, and mutant homozygotes as del/del.