Many mutations have been found in the gene coding for D-BP(HSD17B4)on the q arm two of chromosome five (5q2) in Homo sapiens, most notably individuals homozygous for a missense mutation (616S).
Homozygous mutations in the HAX1 gene are associated with Kostmann disease, i.e. the "classical," autosomal recessive form of severe congenital neutropenia (SCN3).
Western blot analysis shows that homozygous cycle0 mutants have very little PER and TIM protein as well as low per and tim mRNA levels.
Whippets with a homozygous deletion were apparently less able runners although their overall appearance was significantly more muscular.
DNA sequencing revealed that the affected foal was homozygous for a missense mutation in the gene encoding CLCN1, a protein which regulates the excitability of the skeletal muscle.
In Siamese fighting fish the steel blue color comes from being homozygous for a single gene.